PET imaging with PD-L1 binding polypeptides

ABSTRACT

Provided herein are novel 10Fn3 domains which specifically bind to PD-L1, as well as imaging agents based on the same for diagnostics.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 U.S.C. 371 national stage filing of International Application No. PCT/US2017/035227, filed May 31, 2017, which claims priority to U.S. Provisional Application No. 62/344,258, filed Jun. 1, 2016. The contents of the aforementioned applications are hereby incorporated by reference.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has been submitted via EFS-Web and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Nov. 26, 2018, is named MXI-549US_Sequence_Listing.txt and is 457,752 bytes in size.

BACKGROUND

Programmed Death Ligand-1 (PD-L1) is a surface glycoprotein ligand for PD-1, a key immune checkpoint, receptor expressed by activated T and B cells and mediates immunosuppression, which is found on both antigen-presenting cells and human cancers and downregulates T cell activation and cytokine secretion by binding to PD-1 (Freeman et al., 2000; Latchman et al, 2001). Inhibition of the PD-L1/PD-1 interaction allows for potent anti-tumor activity in preclinical models, and antibodies that disrupt this interaction have entered clinical trials for the treatment of cancer (U.S. Pat. Nos. 8,008,449 and 7,943,743; Brahmer et al., 2010; Topalian et al., 2012b; Brahmer et al., 2012; Flies et al. 2011; Pardon 2012; Hamid and Carvajal, 2013).

PET, or Positron Emission Tomography, is a non-invasive, nuclear medicine technique that produces a three-dimensional image of various molecular processes within the body, or the location of proteins associated with disease pathology. The methodology detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer) introduced into the body on a biologically active molecule. PET imaging tools have a wide variety of uses for drug development and have a unique translational medicine advantage, in that the same tool could be used both preclinically and clinically. Examples include direct visualization of in vivo saturation of targets; monitoring uptake in normal tissues to anticipate toxicity or patient to patient variation; quantifying diseased tissue; tumor metastasis; monitoring drug efficacy over time, or resistance over time, and more.

Described herein are novel anti-PD-L1 Adnectins suitable for use as diagnostic/imaging agents, for example, for use in positron emission tomography.

SUMMARY

The present invention is based, at least in part, on the discovery of new anti-human PD-L1 Adnectins which are useful as diagnostic/imaging agents, for example, for use in positron emission tomography, and its methods of administration to subjects. These agents are useful in, e.g., the differentiation of PD-L1 expressing cells from non-PD-L1 expressing cells, e.g., tumor cells or tumor infiltrating lymphocytes (TILs), and the differentiation of PD-L1 expressing tissue from non-PD-L1 expressing tissue, e.g., cancer tissue.

In one aspect, provided herein is a polypeptide comprising a fibronectin type III tenth domain (¹⁰Fn3), wherein (a) the ¹⁰Fn3 domain comprises AB, BC, CD, DE, EF, and FG loops, (b) the ¹⁰Fn3 has at least one loop selected from loop BC, DE, and FG with an altered amino acid sequence relative to the sequence of the corresponding loop of the human ¹⁰Fn3 domain (SEQ ID NO: 1), and (c) the polypeptide specifically binds to PD-L1. In certain embodiments, the polypeptide binds to PD-L1 with a K_(D) of 500 mM or less, for example, 100 mM or less.

In certain embodiments, the ¹⁰Fn3 domain comprises BC, DE, and FG loops comprising the amino acid sequences of:

-   -   (1) SEQ ID NOs: 6, 7, and 8, respectively;     -   (2) SEQ ID NOs: 21, 22, and 23, respectively;     -   (3) SEQ ID NOs: 36, 37, and 38, respectively;     -   (4) SEQ ID NOs: 51, 52, and 53, respectively;     -   (5) SEQ ID NOs: 66, 67, and 68, respectively;     -   (6) SEQ ID NOs: 81, 82, and 83, respectively;     -   (7) SEQ ID NOs: 97, 98, and 99, respectively;     -   (8) SEQ ID NOs: 113, 114, and 115, respectively;     -   (9) SEQ ID NOs: 124, 125 and 126, respectively;     -   (10) SEQ ID NOs: 135, 136 and 137, respectively;     -   (11) SEQ ID NOs: 146, 147 and 148, respectively;     -   (12) SEQ ID NOs: 157, 158 and 159, respectively;     -   (13) SEQ ID NOs: 168, 169 and 170, respectively;     -   (14) SEQ ID NOs: 179, 180 and 181, respectively;     -   (15) SEQ ID NOs: 190, 191 and 192, respectively;     -   (16) SEQ ID NOs: 201, 202 and 203, respectively;     -   (17) SEQ ID NOs: 212, 213 and 214, respectively;     -   (18) SEQ ID NOs: 223, 224 and 225, respectively;     -   (19) SEQ ID NOs: 234, 235, and 236, respectively;     -   (20) SEQ ID NOs: 245, 246 and 247, respectively;     -   (21) SEQ ID NOs: 256, 257 and 258, respectively;     -   (22) SEQ ID NOs: 267, 268 and 269, respectively;     -   (23) SEQ ID NOs: 278, 279 and 280, respectively;     -   (24) SEQ ID NOs: 289, 290 and 291, respectively;     -   (25) SEQ ID NOs: 300, 301 and 302, respectively;     -   (26) SEQ ID NOs: 311, 312 and 313, respectively;     -   (27) SEQ ID NOs: 322, 323 and 324, respectively;     -   (28) SEQ ID NOs: 333, 334 and 335, respectively;     -   (29) SEQ ID NOs: 344, 345 and 346, respectively;     -   (30) SEQ ID NOs: 355, 356 and 357, respectively;     -   (31) SEQ ID NOs: 366, 367 and 368, respectively;     -   (32) SEQ ID NOs: 377, 378 and 379, respectively;     -   (33) SEQ ID NOs: 388, 389 and 390 respectively;     -   (34) SEQ ID NOs: 399, 400 and 401, respectively;     -   (35) SEQ ID NOs: 410, 411 and 412, respectively;     -   (36) SEQ ID NOs: 421, 422 and 423, respectively;     -   (37) SEQ ID NOs: 432, 433 and 434 respectively;     -   (38) SEQ ID NOs: 443, 444 and 445, respectively;     -   (39) SEQ ID NOs: 454, 455 and 456, respectively;     -   (40) SEQ ID NOs: 465, 466 and 467, respectively;     -   (41) SEQ ID NOs: 476, 477 and 478, respectively;     -   (42) SEQ ID NOs: 487, 488 and 489, respectively;     -   (43) SEQ ID NOs: 498, 499 and 500, respectively;     -   (44) SEQ ID NOs: 509, 510 and 511, respectively;     -   (45) SEQ ID NOs: 520, 521 and 522, respectively;     -   (46) SEQ ID NOs: 531, 530 and 531, respectively;     -   (47) SEQ ID NOs: 542, 543 and 544, respectively;     -   (48) SEQ ID NOs: 553, 554 and 555, respectively; or     -   (49) SEQ ID NOs: 564, 565 and 566, respectively.

In certain embodiments, the polypeptide comprises an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to a sequence set forth in Table 3, e.g, any one of SEQ ID NO: 5, 20, 35, 50, 65, 80, 96, 112, 123, 134, 145, 156, 167, 178, 189, 200, 211, 222, 233, 244, 255, 266, 277, 288, 299, 310, 321, 332, 343, 354, 365, 376, 387, 398, 409, 420, 431, 442, 453, 464, 475, 486, 497, 508, 519, 530, 541, 552 and 563. In certain embodiments, the polypeptide comprises an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to the non-BC, DE, and FG loop regions of SEQ ID NO: 5, 20, 35, 50, 65, 80, 96, 112, 123, 134, 145, 156, 167, 178, 189, 200, 211, 222, 233, 244, 255, 266, 277, 288, 299, 310, 321, 332, 343, 354, 365, 376, 387, 398, 409, 420, 431, 442, 453, 464, 475, 486, 497, 508, 519, 530, 541, 552 or 563. In certain embodiments, the polypeptide comprises an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to an amino acid sequence selected from the group consisting of: SEQ ID NOs: 9-15, 24-30, 39-45, 54-60, 69-75, 84-91, 100-107, 116-122, 127-133, 138-144, 150-155, 160-166, 171-177, 182-188, 193-199, 204-210, 215-221, 227-232, 237-243, 248-254, 259-265, 271-276, 291-287, 292-298, 303-309, 314-320, 325-331, 337-342, 347-353, 358-364, 369-375, 380-386, 391-397, 402-408, 413-419, 424-430, 435-441, 446-452, 457-463, 468-474, 479-485, 490-496, 501-507, 512-518, 523-529, 534-540, 545-551, and 556-562. In certain embodiments, the polypeptide comprises an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to the non-BC, DE, and FG loop regions of an amino acid sequence selected from the group consisting of: SEQ ID NOs: 9-15, 24-30, 39-45, 54-60, 69-75, 84-91, 100-107, 116-122, 127-133, 138-144, 150-155, 160-166, 171-177, 182-188, 193-199, 204-210, 215-221, 227-232, 237-243, 248-254, 259-265, 271-276, 291-287, 292-298, 303-309, 314-320, 325-331, 337-342, 347-353, 358-364, 369-375, 380-386, 391-397, 402-408, 413-419, 424-430, 435-441, 446-452, 457-463, 468-474, 479-485, 490-496, 501-507, 512-518, 523-529, 534-540, 545-551, and 556-562.

In certain embodiments, the polypeptide comprises an N-terminal leader selected from the group consisting of SEQ ID NOs: 574-583, and/or a C-terminal tail selected from the group consisting of SEQ ID NOs: 584-618 or PmCn, wherein P is proline, and wherein m is an integer that is at least 0 (e.g., 0, 1 or 2) and n is an integer of at least 1 (e.g., 1 or 2).

In certain embodiments, the polypeptide comprises one or more pharmacokinetic (PK) moieties selected from the group consisting of polyethylene glycol, sialic acid, Fc, Fc fragment, transferrin, serum albumin, a serum albumin binding protein, and a serum immunoglobulin binding protein. In certain embodiments, the PK moiety and the polypeptide are linked via at least one disulfide bond, a peptide bond, a polypeptide, a polymeric sugar or a polyethylene glycol moiety. In certain embodiments, the PK moiety and the polypeptide are linked via a linker with an amino acid sequence selected from the group consisting of SEQ ID NOs: 629-678.

Provided herein are nucleic acids encoding the polypeptides, as well as vectors and cells comprising the nucleic acids, described herein. In certain embodiments, the nucleic acid comprises a nucleotide sequence selected from the group consisting of SEQ ID NOs: 16-19, 31-34, 46-49, 61-64, 76-79, 92-95, and 108-111.

Provided herein are compositions comprising the polypeptides described herein, and a carrier. For example, the compositions described herein comprise a polypeptide comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 5, 9-15, 20, 24-30, 35, 39-45, 50, 54-60, 65, 69-75, 80, 84-91, 96, 100-107, 112, 116-122, 123, 127-133, 134, 138-144, 145, 150-155, 156, 160-166, 167, 171-177, 178, 182-188, 189, 193-199, 200, 204-210, 211, 215-221, 222, 227-232, 233, 237-243, 244, 248-254, 255, 259-265, 266, 271-276, 277, 291-287, 288, 292-298, 299, 303-309, 310, 314-320, 321, 325-331, 332, 337-342, 343, 347-353, 354, 358-364, 365, 369-375, 376, 380-386, 387, 391-397, 398, 402-408, 409, 413-419, 420, 424-430, 431, 435-441, 442, 446-452, 453, 457-463, 464, 468-474, 475, 479-485, 486, 490-496, 497, 501-507, 508, 512-518, 519, 523-529, 530, 534-540, 541, 545-551, 552, and 556-562, and a carrier.

Provided herein are imaging agents comprising the polypeptide disclosed herein. In certain embodiments, the imaging agent comprises a polypeptide comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 5, 9-15, 20, 24-30, 35, 39-45, 50, 54-60, 65, 69-75, 80, 84-91, 96, 100-107, 112, 116-122, 123, 127-133, 134, 138-144, 145, 150-155, 156, 160-166, 167, 171-177, 178, 182-188, 189, 193-199, 200, 204-210, 211, 215-221, 222, 227-232, 233, 237-243, 244, 248-254, 255, 259-265, 266, 271-276, 277, 291-287, 288, 292-298, 299, 303-309, 310, 314-320, 321, 325-331, 332, 337-342, 343, 347-353, 354, 358-364, 365, 369-375, 376, 380-386, 387, 391-397, 398, 402-408, 409, 413-419, 420, 424-430, 431, 435-441, 442, 446-452, 453, 457-463, 464, 468-474, 475, 479-485, 486, 490-496, 497, 501-507, 508, 512-518, 519, 523-529, 530, 534-540, 541, 545-551, 552, and 556-562.

In certain embodiments, the imaging agent comprises a detectable label. In certain embodiments, the imaging agent comprises a polypeptide disclosed herein, a chelating agent, and a detectable label. In certain embodiments, the imaging agent comprises a polypeptide disclosed herein, a bifunctional chelator or conjugating (BFC) moiety and a detectable label. In certain embodiments, the detectable label is a prosthetic group containing a radionuclide. In certain embodiments, the detectable label is detectable by positron emission tomography.

In certain embodiments, the chelating agent and/or bifunctional chelator or conjugating (BFC) moiety is selected from the group consisting of DFO, DOTA, CB-DO2A, 3p-C-DEPA, TCMC, DBCO, DIBO, BARAC, DIMAC, Oxo-DO3A, TE2A, CB-TE2A, CB-TE1A1P, CB-TE2P, MM-TE2A, DM-TE2A, diamsar, NODASA, NODAGA, NOTA, NETA, TACN-TM, DTPA, 1B4M-DTPA, CHX-A″-DTPA, TRAP, NOPO, AAZTA, DATA, H₂dedpa, H₄octapa, H₂azapa, H₅decapa, H₆phospa, HBED, SHBED, BPCA, CP256, PCTA, HEHA, PEPA, EDTA, TETA, and TRITA.

In certain embodiments, the detectable label is a radionuclide, for example,

⁶⁴Cu, ¹²⁴I, ^(76/77)Br, ⁸⁶Y, ⁸⁹Zr, ⁶⁸Ga, ¹⁸F, ¹¹C, ¹²⁵I, ¹²⁴I, ¹³¹I, ¹²³I, ¹³¹I, ¹²³I, ³²Cl, ³³Cl, ³⁴Cl, ⁶⁸Ga, ⁷⁴Br, ⁷⁵Br, ⁷⁶Br, ⁷⁷Br, ⁷⁸Br, ⁸⁹Zr, ¹⁸⁶Re, ¹⁸⁸Re, ⁹⁰Y, ¹⁷⁷Lu, ⁹⁹Tc, or ¹⁵³Sm.

In certain embodiments, the chelating agent is NODAGA and the radionuclide is ⁶⁴Cu. In certain embodiments, the imaging agent comprises an anti-PD-L1 polypeptide (e.g., an anti-PD-L1 Adnectin described herein, e.g., an anti-PD-L1 Adnectin comprising the amino acid sequence set forth in SEQ ID NO: 80 or 96), the chelating agent NODAGA, and the radionuclide ⁶⁴Cu.

In certain embodiments, the imaging agent comprises an anti-PD-L1 polypeptide (e.g., an anti-PD-L1 Adnectin described herein, e.g., an anti-PD-L1 Adnectin comprising the amino acid sequence set forth in SEQ ID NO: 80 or 96), a bifunctional chelator or conjugating (BFC) moiety, and a prosthetic group comprising the radionuclide ¹⁸F. In certain embodiments, the imaging agent has the following structure:

or a pharmaceutically acceptable salt thereof.

In certain embodiments, the imaging agent has the following structure:

In some embodiments, the BFC is a cyclooctyne comprising a reactive group that forms a covalent bond with an amine, carboxyl, carbonyl or thiol functional group on the protein. In some embodiments, the cyclooctyne is selected from the group consisting of dibenzocyclooctyne (DIEM), biarylazacyclooctynone (BARAC), dimethoxyazacyclooctyne (DIMAC) and dibenzocyclooctyne (DBCO). In some embodiments, the cyclooctyne is DBCO.

In some embodiments, the BFC is DBCO-PEG4-NHS-Ester, DBCO-Sulfo-NHS-Ester, DBCO-PEG4-Acid, DBCO-PEG4-Amine or DBCO-PEG4-Maleimide. In some embodiments, the BFC is DBCO-PEG4-Maleimide.

In certain embodiments, the imaging agent has the structure:

wherein X is a polypeptide comprising the amino acid sequence of any one of SEQ ID NOs: 13, 28, 43, 58, 73, 88, 104, 120, 131, 142, 153, 164, 175, 186, 197, 208, 219, 230, 241, 252, 263, 274, 285, 296, 307, 318, 329, 340, 351, 362, 373, 384, 395, 406, 417, 428, 439, 450, 461, 472, 483, 494, 505, 516, 527, 538, 549, 560 and 571. In certain embodiments, the polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 88. In certain embodiments, thepolypeptide comprises the amino acid sequence set forth in SEQ ID NO: 104.

Provided herein are kits comprising an anti-PD-L1 Adnectin composition and/or imaging agent described herein, and instructions for use.

Provided herein is a method of detecting PD-L1 in a sample, the method comprising contacting the sample with an anti-PD-L1 Adnectin, and detecting PD-L1.

Provided herein is a method of detecting PD-L1 positive cells in a subject comprising administering to the subject an imaging agent comprising an anti-PD-L1 Adnectin, and detecting the imaging agent, the detected imaging agent defining the location of the PD-L1 positive cells in the subject.

Provided herein is a method of detecting PD-L1-expressing tumors in a subject comprising administering to the subject an imaging agent comprising an anti-PD-L1 Adnectin, and detecting the imaging agent, the detected imaging agent defining the location of the tumor in the subject. In certain embodiments, the imaging agent is detected by positron emission tomography.

Provided herein is a method of obtaining an image of an imaging agent comprising an anti-PD-L1 Adnectin, the method comprising,

-   -   a) administering the imaging agent to a subject; and     -   b) imaging in vivo the distribution of the imaging agent by         positron emission tomography.

Provided herein is a method of obtaining a quantitative image of tissues or cells expressing PD-L1, the method comprising contacting the cells or tissue with an imaging agent comprising an anti-PD-L1 Adnectin, and detecting or quantifying the tissue expressing PD-L1 using positron emission tomography.

Provided herein is a method for detecting a PD-L1-expressing tumor comprising administering an imaging-effective amount of an imaging agent comprising an anti-PD-L1 Adnectin to a subject having a PD-L1-expressing tumor, and detecting the radioactive emissions of said imaging agent in the tumor using positron emission tomography, wherein the radioactive emissions are detected in the tumor.

Provided herein is a method of diagnosing the presence of a PD-L1-expressing tumor in a subject, the method comprising

-   -   (a) administering to a subject in need thereof an imaging agent         comprising an anti PD-L1 Adnectin; and     -   (b) obtaining a radio-image of at least a portion of the subject         to detect the presence or absence of the imaging agent;         wherein the presence and location of the imaging agent above         background is indicative of the presence and location of a PD-L1         expressing tumor in the subject.

Provided herein is a method of treating a subject having cancer, comprising

-   -   (a) administering to a subject in need thereof an imaging agent         comprising an anti-PD-L1 Adnectin, and obtaining an image of at         least a portion of the subject to determine the presence of         PD-L1 in one or more tumors; and, if PD-L1 is detected in one or         more tumors, then,     -   (b) administering an anti-tumor therapy, e.g., an agent that         inhibits the interaction between PD-1 and PD-L1 (a PD-1 or PD-L1         antagonist) to the subject.

Provided herein is a method of monitoring the progress of an anti-tumor therapy against PD-L1-expressing tumors in a subject, the method comprising

-   -   (a) administering to a subject in need thereof an imaging agent         comprising an anti-PD-L1 Adnectin at a first time point and         obtaining an image of at least a portion of the subject to         determine the size of the tumor;     -   (b) administering an anti-tumor therapy to the subject;     -   (c) administering to the subject the imaging agent at one or         more subsequent time points and obtaining an image of at least a         portion of the subject at each time point; wherein the dimension         and location of the tumor at each time point is indicative of         the progress of the disease.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the core amino acid sequences of exemplary anti-PD-L1 Adnectins described herein. The BC, DE, and FG loops are underlined. Wildtype (WT) (SEQ ID NO: 2), ATI-968 (SEQ ID NO: 5), ATI-964 (SEQ ID NO: 20), ATI-967 (SEQ ID NO: 65), A02 (SEQ ID NO: 80), E01 (SEQ ID NO: 96), ATI-965 (SEQ ID NO: 35), and ATI-966 (SEQ ID NO: 50).

FIG. 2 is a schematic for the chemical synthesis of [¹⁸F]-E01-4PEG-DBCO-FPPEGA. The E01 portion of the molecule has the sequence set forth in SEQ ID NO: 104.

FIG. 3 is a graph demonstrating discrimination of hPD-L1-positive L2987 cells from hPD-L1-negative HT-29 cells with the ⁶⁴Cu-E01 anti-PD-L1 Adnectin (with a NODAGA chelator). Specificity was confirmed by the reduction of cell-associated ⁶⁴Cu-E01 when co-incubated with excess cold (unlabeled) E01 Adnectin.

FIG. 4A is a PET image depicting the discrimination of hPD-L1 (+) from hPD-L1 (−) tumors in bilateral xenograft mice with a NODAGA-⁶⁴Cu-labeled A02 anti-PD-L1 Adnectin. Shown are summed 0 to 2 hour images showing areas of probe residence. Bright areas are tissues of greatest occupancy during exposure.

FIG. 4B is a graph depicting a time course of tumor labeling in hPD-L1 (+) [L2987] tumors. hPD-L1(−) [HT29] tumors and pulse chase experiment in hPD-L1(+) systems [L2987 block] show the specificity of the labelling.

FIG. 5 is a graph depicting tissue distribution of the ¹⁸F-labeled A02 anti-PD-L1 Adnectin radiotracer in mice bearing bilateral hPD-L1(+) L2987 and hPD-L1(−) HT-29 xenografts as measured ex vivo by gamma counter.

FIG. 6 is a composite image of ¹⁸F-labeled E01 anti-PD-L1 Adnectin distribution in cynomolgus monkey.

FIG. 7 is an image depicting in vitro autoradiography of xenograft and human lung tissues labelled with the 0.25 nM ¹⁸F-DBCO-A02 anti-PD-L1 Adnectin co-incubated with the indicated concentrations of cold A02 Adnectin.

FIG. 8 depicts immunohistochemistry images of xenograft and human lung tumor specimens labelled with anti-PD-L1 Adnectins to demonstrate tumor expression of hPD-L1.

FIG. 9 shows a reaction scheme for synthesizing [¹⁸F]-A02-4PEG-DBCO-FPPEGA. The same reaction scheme was used to label the E01 adnectin.

FIG. 10 is a schematic of the GE TRACERlab FX2 N Synthesis module for automated synthesis of [¹⁸F]-FPPEGA.

FIG. 11 is a schematic of the Synthera Synthesis module (IBA) for automated synthesis of [¹⁸F]-FPPEGA.

FIG. 12 depicts exemplary competition curves of anti-PD-L1 Adnectins.

DETAILED DESCRIPTION Definitions

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by the skilled artisan. Although any methods and compositions similar or equivalent to those described herein can be used in practice or testing of the present invention, the preferred methods and compositions are described herein.

“Programmed Death Ligand-1 (PD-L1)” is one of two cell surface glycoprotein ligands for PD-1 (the other being PD-L2) that downregulate T cell activation and cytokine secretion upon binding to PD-1. The term “PD-L1” as used herein includes human PD-L1 (hPD-L1), variants, isoforms, and species homologs of hPD-L1, and analogs having at least one common epitope with hPD-L1. The complete hPD-L1 sequence can be found under GenBank Accession No, Q9NZQ7. PD-L1 is also referred to as CD274, B7-H, B7H1, PDCD1L1, and PDCD1LG1.

“Polypeptide” as used herein refers to any sequence of two or more amino acids, regardless of length, post-translation modification, or function. Polypeptides can include natural amino acids and non-natural amino acids such as those described in U.S. Pat. No. 6,559,126, incorporated herein by reference. Polypeptides can also be modified in any of a variety of standard chemical ways (e.g., an amino acid can be modified with a protecting group; the carboxy-terminal amino acid can be made into a terminal amide group; the amino-terminal residue can be modified with groups to, e.g., enhance lipophilicity; or the polypeptide can be chemically glycosylated or otherwise modified to increase stability or in vivo half-life). Polypeptide modifications can include the attachment of another structure such as a cyclic compound or other molecule to the polypeptide and can also include polypeptides that contain one or more amino acids in an altered configuration (i.e., R or S; or, L or D). The peptides described herein are proteins derived from the tenth type III domain of fibronectin that have been modified to bind specifically to human PD-L1 and are referred to herein as, “anti-PD-L1 Adnectin” or “PD-L1 Adnectin.”

A “polypeptide chain,” as used herein, refers to a polypeptide wherein each of the domains thereof is joined to other domain(s) by peptide bond(s), as opposed to non-covalent interactions or disulfide bonds.

An “isolated” polypeptide is one that has been identified and separated and/or recovered from a component of its natural environment. Contaminant components of its natural environment are materials that would interfere with diagnostic or therapeutic uses for the polypeptide, and may include enzymes, hormones, and other proteinaceous or nonproteinaceous solutes. In preferred embodiments, the polypeptide will be purified (1) to greater than 95% by weight of polypeptide as determined by the Lowry method, and most preferably more than 99% by weight, (2) to a degree sufficient to obtain at least residues of N-terminal or internal amino acid sequence by use of a spinning cup sequenator, or (3) to homogeneity by SDS-PAGE under reducing or nonreducing condition using Coomassie blue or, preferably, silver stain. Isolated polypeptide includes the polypeptide in situ within recombinant cells since at least one component of the polypeptide's natural environment will not be present. Ordinarily, however, isolated polypeptide will be prepared by at least one purification step.

A “region” of a ¹⁰Fn3 domain as used herein refers to either a loop (AB, BC, CD, DE, EF and FG), a β-strand (A, B, C, D, E, F and G), the N-terminus (corresponding to amino acid residues 1-7 of SEQ ID NO: 1), or the C-terminus (corresponding to amino acid residues 93-94 of SEQ ID NO: 1) of the human ¹⁰Fn3 domain.

A “scaffold region” refers to any non-loop region of a human ¹⁰Fn3 domain. The scaffold region includes the A, B, C, D, E, F and G β-strands as well as the N-terminal region (amino acids corresponding to residues 1-7 of SEQ ID NO: 1) and the C-terminal region (amino acids corresponding to residues 93-94 of SEQ ID NO: 1 and optionally comprising the 7 amino acids constituting the natural linker between the 10^(th) and the 11^(th) repeat of the Fn3 domain in human fibronectin).

“Percent (%) amino acid sequence identity” herein is defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in a selected sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Alignment for purposes of determining percent amino acid sequence identity can be achieved in various ways that are within the skill in the art, for instance, using publicly available computer software such as BLAST, BLAST-2, ALIGN, ALIGN-2 or Megalign (DNASTAR™) software. Those skilled in the art can readily determine appropriate parameters for measuring alignment, including any algorithms needed to achieve maximal alignment over the full-length of the sequences being compared. For example, the % amino acid sequence identity of a given amino acid sequence A to, with, or against a given amino acid sequence B (which can alternatively be phrased as a given amino acid sequence A that has or comprises a certain % amino acid sequence identity to, with, or against a given amino acid sequence B) is calculated as follows: 100 times the fraction X/Y where X is the number of amino acid residues scored as identical matches by the sequence alignment program ALIGN-2 in that program's alignment of A and B, and where Y is the total number of amino acid residues in B. It will be appreciated that where the length of amino acid sequence A is not equal to the length of amino acid sequence B, the % amino acid sequence identity of A to B will not equal the % amino acid sequence identity of B to A.

As used herein, the term “Adnectin binding site” refers to the site or portion of a protein (e.g., PD-L1) that interacts or binds to a particular Adnectin. Adnectin binding sites can be formed from contiguous amino acids or noncontiguous amino acids juxtaposed by tertiary folding of a protein. Adnectin binding sites formed by contiguous amino acids are typically retained on exposure to denaturing solvents, whereas Adnectin binding sites formed by tertiary folding are typically lost on treatment of denaturing solvents.

An Adnectin binding site for an anti-PD-L1 Adnectin described herein may be determined by application of standard techniques typically used for epitope mapping of antibodies including, but not limited to protease mapping and mutational analysis. Alternatively, an Adnectin binding site can be determined by competition assay using a reference Adnectin or antibody which binds to the same polypeptide, e.g., PD-L1 (as further described infra in the section “Cross-Competing Adnectins and/or Adnectins that Bind to the Same Adnectin Binding Site.” If the test Adnectin and reference molecule (e.g., another Adnectin or antibody) compete, then they bind to the same Adnectin binding site or to Adnectin binding sites sufficiently proximal such that binding of one molecule interferes with the other. An Adnectin binding site is defined by the method used to identify it. For example, an Adnectin may bind to a given binding site, as determined via HDX; an Adnectin may bind to a given binding site, as determined via crystallography; or an Adnectin may bind go to a given binding site as determined by directed mutational analysis.

The terms “specifically binds,” “specific binding,” “selective binding, and “selectively binds,” as used interchangeably herein in the context of Adnectins binding to PD-L1 refers to an Adnectin that exhibits affinity for PD-L1, but does not significantly bind (e.g., less than about 10% binding) to a different polypeptides as measured by a technique available in the art such as, but not limited to, Scatchard analysis and/or competitive binding assays (e.g., competition ELISA, BIACORE assay). The term is also applicable where e.g., a binding domain of an Adnectin described herein is specific for PD-L1.

The term “preferentially binds” as used herein in the context of Adnectins binding to PD-L1 refers to the situation in which an Adnectin described herein binds PD-L1 at least about 20% greater than it binds a different polypeptide as measured by a technique available in the art such as, but not limited to, Scatchard analysis and/or competitive binding assays (e.g., competition ELISA, BIACORE assay).

As used herein in the context of Adnectins, the term “cross-reactivity” refers to an Adnectin which binds to more than one distinct protein having identical or very similar Adnectin binding sites.

The term “K_(D),” as used herein in the context of Adnectins binding to PD-L1, is intended to refer to the dissociation equilibrium constant of a particular Adnectin-protein (e.g., PD-L1) interaction or the affinity of an Adnectin for a protein (e.g., PD-L1), as measured using a surface plasmon resonance assay or a cell binding assay. A “desired K_(D),” as used herein, refers to a K_(D) of an Adnectin that is sufficient for the purposes contemplated. For example, a desired K_(D) may refer to the K_(D) of an Adnectin required to elicit a functional effect in an in vitro assay, e.g., a cell-based luciferase assay.

The term “k_(a)”, as used herein in the context of Adnectins binding to a protein, is intended to refer to the association rate constant for the association of an Adnectin into the Adnectin/protein complex.

The term “k_(d)”, as used herein in the context of Adnectins binding to a protein, is intended to refer to the dissociation rate constant for the dissociation of an Adnectin from the Adnectin/protein complex.

The term “IC₅₀”, as used herein in the context of Adnectins, refers to the concentration of an Adnectin that inhibits a response, either in an in vitro or an in vivo assay, to a level that is 50% of the maximal inhibitory response, i.e., halfway between the maximal inhibitory response and the untreated response.

The term “PK” is an acronym for “pharmacokinetic” and encompasses properties of a compound including, by way of example, absorption, distribution, metabolism, and elimination by a subject. A “PK modulation protein” or “PK moiety” as used herein refers to any protein, peptide, or moiety that affects the pharmacokinetic properties of a biologically active molecule when fused to or administered together with the biologically active molecule. Examples of a PK modulation protein or PK moiety include PEG, human serum albumin (HSA) binders (as disclosed in U.S. Publication Nos. 2005/0287153 and 2007/0003549, PCT Publication Nos. WO 2009/083804 and WO 2009/133208), human serum albumin and variants thereof, transferrin and variants thereof, Fc or Fc fragments and variants thereof, and sugars (e.g., sialic acid).

The “serum half-life” of a protein or compound is the time taken for the serum concentration of the polypeptide to be reduced by 50%, in vivo, for example due to degradation of the sequence or compound and/or clearance or sequestration of the sequence or compound by natural mechanisms. The half-life can be determined in any manner known per se, such as by pharmacokinetic analysis. Suitable techniques will be clear to the person skilled in the art, and may for example generally involve the steps of suitably administering to a subject a suitable dose of the amino acid sequence or compound described herein; collecting blood samples or other samples from the subject at regular intervals; determining the level or concentration of the amino acid sequence or compound described herein in said blood sample; and calculating, from (a plot of) the data thus obtained, the time until the level or concentration of the amino acid sequence or compound described herein has been reduced by 50% compared to the initial level upon dosing. Reference is, for example, made to the standard handbooks, such as Kenneth, A. et al., Chemical Stability of Pharmaceuticals: A Handbook for Pharmacists and in Peters et al., Pharmacokinete Analysis: A Practical Approach (1996). Reference is also made to Gibaldi, M. et al., Pharmacokinetics, 2nd Rev. Edition, Marcel Dekker (1982).

Half-life can be expressed using parameters such as the t_(1/2)-alpha, t_(1/2)-beta, HL_Lambda_z, and the area under the curve (AUC).

The term “detectable” refers to the ability to detect a signal over the background signal. The term “detectable signal” is a signal derived from non-invasive imaging techniques such as, but not limited to, positron emission tomography (PET). The detectable signal is detectable and distinguishable from other background signals that may be generated from the subject. In other words, there is a measurable and statistically significant difference (e.g., a statistically significant difference is enough of a difference to distinguish among the detectable signal and the background, such as about 0.1%, 1%, 3%, 5%, 10%, 15%, 20%, 25%, 30%, or 40% or more difference between the detectable signal and the background) between the detectable signal and the background. Standards and/or calibration curves can be used to determine the relative intensity of the detectable signal and/or the background.

A “detectably effective amount” of a composition comprising an imaging agent described herein is defined as an amount sufficient to yield an acceptable image using equipment that is available for clinical use. A detectably effective amount of an imaging agent provided herein may be administered in more than one injection. The detectably effective amount can vary according to factors such as the degree of susceptibility of the individual, the age, sex, and weight of the individual, idiosyncratic responses of the individual, and the like. Detectably effective amounts of imaging compositions can also vary according to instrument and methodologies used. Optimization of such factors is well within the level of skill in the art. In certain embodiments, a PD-L1 imaging agent, e.g., those described herein, provides a differentiation factor (i.e., specific signal to background signal) of 2 or more, e.g., 3, 4, 5 or more.

The term “bioorthogonal chemistry” refers to any chemical reaction that can occur inside of living systems without interfering with native biochemical processes. The term includes chemical reactions that are chemical reactions that occur in vitro at physiological pH in, or in the presence of water. To be considered bioorthogonol, the reactions are selective and avoid side-reactions with other functional groups found in the starting compounds. In addition, the resulting covalent bond between the reaction partners should be strong and chemically inert to biological reactions and should not affect the biological activity of the desired molecule.

The term “click chemistry” refers to a set of reliable and selective bioorthogonal reactions for the rapid synthesis of new compounds and combinatorial libraries. Properties of for click reactions include modularity, wideness in scope, high yielding, stereospecificity and simple product isolation (separation from inert by-products by non-chromatographic methods) to produce compounds that are stable under physiological conditions. In radiochemistry and radiopharmacy, click chemistry is a generic term for a set of labeling reactions which make use of selective and modular building blocks and enable chemoselective ligations to radiolabel biologically relevant compounds in the absence of catalysts. A “click reaction” can be with copper, or it can be a copper-free click reaction.

The term “prosthetic group” or “bifunctional labeling agent” refers to a small organic molecule containing a radionulide (e.g., ¹⁸F) that is capable of being linked to peptides or proteins.

The term “chelator ligand” as used herein with respect to radiopharmaceutical chemistry refers to a bifunctional chelator or conjugating (BFC) moiety, which are used interchangeably herein, that covalently links a radiolabeled prosthetic group to a biologically active targeting molecule (e.g., peptide or protein). BFCs utilize functional groups such as carboxylic acids or activated esters for amide couplings, isothiocyanates for thiourea couplings and maleimides for thiol couplings.

The terms “individual,” “subject,” and “patient,” used interchangeably herein, refer to a human.

A “cancer” refers a broad group of various diseases characterized by the uncontrolled growth of abnormal cells in the body. Unregulated cell division and growth divide and grow results in the formation of malignant tumors that invade neighboring tissues and may also metastasize to distant parts of the body through the lymphatic system or bloodstream.

An “immune response” refers to the action of a cell of the immune system (for example, T lymphocytes, B lymphocytes, natural killer (NK) cells, macrophages, eosinophils, mast cells, dendritic cells and neutrophils) and soluble macromolecules produced by any of these cells or the liver (including Abs, cytokines, and complement) that results in selective targeting, binding to, damage to, destruction of, and/or elimination from a vertebrate's body of invading pathogens, cells or tissues infected with pathogens, cancerous or other abnormal cells, or, in cases of autoimmunity or pathological inflammation, normal human cells or tissues.

An “immunoregulator” refers to a substance, an agent, a signaling pathway or a component thereof that regulates an immune response. “Regulating,” “modifying” or “modulating” an immune response refers to any alteration in a cell of the immune system or in the activity of such cell. Such regulation includes stimulation or suppression of the immune system which may be manifested by an increase or decrease in the number of various cell types, an increase or decrease in the activity of these cells, or any other changes which can occur within the immune system. Both inhibitory and stimulatory immunoregulators have been identified, some of which may have enhanced function in the cancer microenvironment.

The term “immunotherapy” refers to the treatment of a subject afflicted with, or at risk of contracting or suffering a recurrence of, a disease by a method comprising inducing, enhancing, suppressing or otherwise modifying an immune response.

“Treatment” or “therapy” of a subject refers to any type of intervention or process performed on, or the administration of an active agent to, the subject with the objective of reversing, alleviating, ameliorating, inhibiting, slowing down or preventing the onset, progression, development, severity or recurrence of a symptom, complication, condition or biochemical indicia associated with a disease.

“Administration” or “administering,” as used herein in the context of anti-PD-L1 Adnectins, refers to introducing a PD-L1 Adnectin or PD-L1 Adnectin-based probe or a labeled probe (also referred to as the “imaging agent”) described herein into a subject. Any route of administration is suitable, such as intravenous, oral, topical, subcutaneous, peritoneal, intra-arterial, inhalation, vaginal, rectal, nasal, introduction into the cerebrospinal fluid, or instillation into body compartments can be used.

The term “therapeutically effective amount” refers to at least the minimal dose, but less than a toxic dose, of an agent which is necessary to impart a therapeutic benefit to a subject.

As used herein, an “effective amount” refers to at least an amount effective, at dosages and for periods of time necessary, to achieve the desired result.

As used herein, a “sufficient amount” refers to an amount sufficient to achieve the desired result.

As used herein, “positron emission tomography” or “PET” refers to a non-invasive, nuclear medicine technique that produces a three-dimensional image of tracer location in the body. The method detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule. PET imaging tools have a wide variety of uses and aid in drug development both preclinically and clinically. Exemplary applications include direct visualization of in vivo saturation of targets; monitoring uptake in normal tissues to anticipate toxicity or patient to patient variation; quantifying diseased tissue; tumor metastasis; and monitoring drug efficacy over time, or resistance over time.

Overview

Provided herein are polypeptides that bind to human PD-L1 and can be coupled to heterologous molecule(s), such as a radiolabel. Such polypeptides are useful, for example, for detecting PD-L1 in a sample or tissue, e.g., in a subject (e.g., a tissue, such as a cancer tissue that selectively expresses PD-L1), e.g., for diagnostic assays.

The invention is based on the development of a non-invasive clinical imaging agent that allows for whole body visualization of a patient's PD-L1 expression. In certain embodiments, single day “virtual biopsies” of a patient's whole body are performed to monitor and localize PD-L1 expression levels. PD-L1 imaging agents described herein may be used to provide a high contrast whole-body virtual biopsy in a single day.

I. FIBRONECTIN-BASED SCAFFOLDS

Fn3 refers to a type III domain from fibronectin. An Fn3 domain is small, monomeric, soluble, and stable. It lacks disulfide bonds and, therefore, is stable under reducing conditions. The overall structure of Fn3 resembles the immunoglobulin fold. Fn3 domains comprise, in order from N-terminus to C-terminus, a beta or beta-like strand, A; a loop, AB; a beta or beta-like strand, B; a loop, BC; a beta or beta-like strand, C; a loop, CD; a beta or beta-like strand, D; a loop, DE; a beta or beta-like strand, E; a loop, EF; a beta or beta-like strand, F; a loop, FG; and a beta or beta-like strand, G. The seven antiparallel β-strands are arranged as two beta sheets that form a stable core, while creating two “faces” composed of the loops that connect the beta or beta-like strands. Loops AB, CD, and EF are located at one face (“the south pole”) and loops BC, DE, and FG are located on the opposing face (“the north pole”). There are at least 15 different Fn3 modules in human Fibronectin, and while the sequence homology between the modules is low, they all share a high similarity in tertiary structure.

Described herein are anti-PD-L1 Adnectins comprising an Fn3 domain in which one or more of the solvent accessible loops has been randomized or mutated. In certain embodiments, the Fn3 domain is an Fn3 domain derived from the wild-type tenth module of the human fibronectin type III domain (¹⁰Fn3):

(SEQ ID NO: 1) VSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITYGETGGNSPVQE FTVPGSKSTATISGLKPGVDYTITVYAVTGRGDSPASSKPISINYRT (94 amino acids; AB, CD, and EF loops are underlined; the core ¹⁰Fn3 domain begins with amino acid 9 (“E”) and ends with amino acid 94 (“T”) and corresponds to an 86 amino acid polypeptide). The core wild-type human ¹⁰Fn3 domain is set forth in SEQ ID NO: 2.

Both variant and wild-type ¹⁰Fn3 proteins are characterized by the same structure, namely seven beta-strand domain sequences designated A through G and six loop regions (AB loop, BC loop, CD loop, DE loop, EF loop, and FG loop) which connect the seven beta-strand domain sequences. The beta strands positioned closest to the N- and C-termini may adopt a beta-like conformation in solution. In SEQ ID NO: 1, the AB loop corresponds to residues 14-17, the BC loop corresponds to residues 23-31, the CD loop corresponds to residues 37-47, the DE loop corresponds to residues 51-56, the EF loop corresponds to residues 63-67, and the FG loop corresponds to residues 75-87.

Accordingly, in certain embodiments, the anti-PD-L1 Adnectin described herein is an ¹⁰Fn3 polypeptide that is at least 40%, 50%, 60%, 65%, 70%, 75%, 80%, 85%, or 90% identical to the human ¹⁰Fn3 domain, shown in SEQ ID NO: 1, or its core sequence, as shown in SEQ ID NO: 2. Much of the variability will generally occur in one or more of the loops or one or more of the beta strands or N- or C-terminal regions. Each of the beta or beta-like strands of a ¹⁰Fn3 polypeptide may consist essentially of an amino acid sequence that is at least 80%, 85%, 90%, 95% or 100% identical to the sequence of a corresponding beta or beta-like strand of SEQ ID NO: 1 or 2, provided that such variation does not disrupt the stability of the polypeptide in physiological conditions.

In certain embodiments, the invention provides an anti-human PD-L1 Adnectin comprising a tenth fibronectin type III (¹⁰Fn3) domain, wherein the ¹⁰Fn3 domain comprises a loop, AB; a loop, BC; a loop, CD; a loop, DE; a loop EF; and a loop FG; and has at least one loop selected from loop BC, DE, and FG with an altered amino acid sequence relative to the sequence of the corresponding loop of the human ¹⁰Fn3 domain. An “Adnectin” is a modified human ¹⁰Fn3 domain that binds to a target that is not bound by the unmodified human ¹⁰Fn3 domain. In some embodiments, the anti-PD-L1 Adnectins described herein comprise a ¹⁰Fn3 domain comprising an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to the non-loop regions of SEQ ID NO: 1 or 2, wherein at least one loop selected from BC, DE, and FG is altered. In certain embodiments, the BC and FG loops are altered, in certain embodiments, the BC and DE loops are altered, in certain embodiments, the DE and FG loops are altered, and in certain embodiments, the BC, DE, and FG loops are altered, i.e., the ¹⁰Fn3 domains comprise non-naturally occurring loops. In certain embodiments, the AB, CD and/or the EF loops are altered. By “altered” is meant one or more amino acid sequence alterations relative to a template sequence (corresponding human fibronectin domain) and includes amino acid additions, deletions, substitutions or a combination thereof. Altering an amino acid sequence may be accomplished through intentional, blind, or spontaneous sequence variation, generally of a nucleic acid coding sequence, and may occur by any technique, for example, PCR, error-prone PCR, or chemical DNA synthesis.

In certain embodiments, one or more loops selected from BC, DE, and FG may be extended or shortened in length relative to the corresponding human fibronectin loop. In some embodiments, the length of the loop may be extended by 2-25 amino acids. In some embodiments, the length of the loop may be decreased by 1-11 amino acids. To optimize antigen binding, therefore, the length of a loop of ¹⁰Fn3 may be altered in length as well as in sequence to obtain the greatest possible flexibility and affinity in antigen binding.

In certain embodiments, the polypeptide comprises a Fn3 domain that comprises an amino acid sequence of the non-loop regions that is at least 80, 85, 90, 95, 98, 99, or 100% identical to the non-loop regions of SEQ ID NO: 1 or 2, wherein at least one loop selected from BC, DE, and FG is altered. In some embodiments, the altered BC loop has up to 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, up to 1, 2, 3, or 4 amino acid deletions, up to 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid insertions, or a combination thereof.

In some embodiments, one or more residues of the integrin-binding motif “arginine-glycine-aspartic acid” (RGD) (amino acids 78-80 of SEQ ID NO: 1) may be substituted so as to disrupt integrin binding. In some embodiments, the FG loop of the polypeptides provided herein does not contain an RGD integrin binding site. In one embodiment, the RGD sequence is replaced by a polar amino acid-neutral amino acid-acidic amino acid sequence (in the N-terminal to C-terminal direction). In some embodiments, the RGD sequence is replaced with SGE. In one embodiment, the RGD sequence is replaced with RGE.

In certain embodiments, the fibronectin based scaffold protein comprises a ¹⁰Fn3 domain that is defined generally by following the sequence:

(SEQ ID NO: 3) EVVAA(Z)_(a) LLISW(Z)_(x) YRITY(Z)_(b) FTV(Z)_(y) ATISGL(Z)_(c) YTITV YA(Z)_(z) ISINYRT wherein the AB loop is represented by (Z)_(a), the CD loop is represented by (Z)_(b), the EF loop is represented by (Z)_(c), the BC loop is represented by (Z)_(x), the DE loop is represented by (Z)_(y), and the FG loop is represented by (Z)_(z). Z represents any amino acid and the subscript following the Z represents an integer of the number of amino acids. In particular, a may be anywhere from 1-15, 2-15, 1-10, 2-10, 1-8, 2-8, 1-5, 2-5, 1-4, 2-4, 1-3, 2-3, or 1-2 amino acids; and b, c, x, y and z may each independently be anywhere from 2-20, 2-15, 2-10, 2-8, 5-20, 5-15, 5-10, 5-8, 6-20, 6-15, 6-10, 6-8, 2-7, 5-7, or 6-7 amino acids. The sequences of the beta strands may have anywhere from 0 to 10, from 0 to 8, from 0 to 6, from 0 to 5, from 0 to 4, from 0 to 3, from 0 to 2, or from 0 to 1 substitutions, deletions or additions across all 7 scaffold regions relative to the corresponding amino acids shown in SEQ ID NO: 1 or 2. In certain embodiments, the sequences of the beta strands may have anywhere from 0 to 10, from 0 to 8, from 0 to 6, from 0 to 5, from 0 to 4, from 0 to 3, from 0 to 2, or from 0 to 1 conservative substitutions across all 7 scaffold regions relative to the corresponding amino acids shown in SEQ ID NO: 1 or 2. In certain embodiments, the core amino acid residues are fixed and any substitutions, conservative substitutions, deletions or additions occur at residues other than the core amino acid residues.

In certain embodiments, the anti-PD-L1 Adnectins described herein are based on a ¹⁰Fn3 scaffold and are defined generally by the sequence:

(SEQ ID NO: 4) EVVAATPTSLLISW(Z)_(x)NRITYGETGGNSPVQEFTV(Z)_(y)ATISGLKP GVDYTITVYA(Z)_(z)ISINYRT. wherein the BC loop is represented by (Z)_(x), the DE loop is represented by (Z)_(y), and the FG loop is represented by (Z)_(z). Z represents any amino acid and the subscript following the Z represents an integer of the number of amino acids. In particular, x, y and z may each independently be anywhere from 2-20, 2-15, 2-10, 2-8, 5-20, 5-15, 5-10, 5-8, 6-20, 6-15, 6-10, 6-8, 2-7, 5-7, or 6-7 amino acids. In preferred embodiments, x is 11 amino acids, y is 6 amino acids, and z is 12 amino acids. The sequences of the beta strands may have anywhere from 0 to 10, from 0 to 8, from 0 to 6, from 0 to 5, from 0 to 4, from 0 to 3, from 0 to 2, or from 0 to 1 substitutions, deletions or additions across all 7 scaffold regions relative to the corresponding amino acids shown in SEQ ID NO: 1 or 2. In certain embodiments, the sequences of the beta strands may have anywhere from 0 to 10, from 0 to 8, from 0 to 6, from 0 to 5, from 0 to 4, from 0 to 3, from 0 to 2, or from 0 to 1 conservative substitutions across all 7 scaffold regions relative to the corresponding amino acids shown in SEQ ID NO: 1 or 2. In certain embodiments, the core amino acid residues, e.g., outside one or more loops, are fixed and any substitutions, conservative substitutions, deletions or additions occur at residues other than the core amino acid residues.

In certain embodiments, an anti-PD-L1 Adnectin may comprise the sequence as set forth in SEQ ID NO: 3 or 4, wherein at least one of BC, DE, and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, are altered. As described above, amino acid residues corresponding to residues 23-31, 51-56, and 75-87 of SEQ ID NO: 1 define the BC, DE, and FG loops, respectively. However, it should be understood that not every residue within the loop region needs to be modified in order to achieve a ¹⁰Fn3 binder having strong affinity for a desired target (e.g., PD-L1).

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, have amino acid sequences at least 75%, 80%, 85%, 90%, 95%, 97%, 98%, or 99% identical to the BC, DE or FG loop sequences set forth in SEQ ID NOs: 21, 22, and 23, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, comprise BC, DE, and FG loops having the amino acid sequences of SEQ ID NOs: 21, 22, and 23, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, have amino acid sequences at least 75%, 80%, 85%, 90%, 95%, 97%, 98%, or 99% identical to the BC, DE or FG loop sequences set forth in SEQ ID NOs: 36, 37, and 38, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, comprise BC, DE, and FG loops having the amino acid sequences of SEQ ID NOs: 36, 37, and 38, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, have amino acid sequences at least 75%, 80%, 85%, 90%, 95%, 97%, 98%, or 99% identical to the BC, DE or FG loop sequences set forth in SEQ ID NOs: 51, 52, and 53, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, comprise BC, DE, and FG loops having the amino acid sequences of SEQ ID NOs: 51, 52, and 53, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, have amino acid sequences at least 75%, 80%, 85%, 90%, 95%, 97%, 98%, or 99% identical to the BC, DE or FG loop sequences set forth in SEQ ID NOs: 66, 67, and 68, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, comprise BC, DE, and FG loops having the amino acid sequences of SEQ ID NOs: 66, 67, and 68, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, have amino acid sequences at least 75%, 80%, 85%, 90%, 95%, 97%, 98%, or 99% identical to the BC, DE or FG loop sequences set forth in SEQ ID NOs: 6, 7, and 8, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, comprise BC, DE, and FG loops having the amino acid sequences of SEQ ID NOs: 6, 7, and 8, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, have amino acid sequences at least 75%, 80%, 85%, 90%, 95%, 97%, 98%, or 99% identical to the BC, DE or FG loop sequences set forth in SEQ ID NOs: 81, 82, and 83, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, comprise BC, DE, and FG loops having the amino acid sequences of SEQ ID NOs: 81, 82, and 83, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, have amino acid sequences at least 75%, 80%, 85%, 90%, 95%, 97%, 98%, or 99% identical to the BC, DE or FG loop sequences set forth in SEQ ID NOs: 97, 98, and 99, respectively. In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, comprise BC, DE, and FG loops having the amino acid sequences of SEQ ID NOs: 97, 98, and 99, respectively.

In certain embodiments, an anti-PD-L1 Adnectin comprises the sequence set forth in SEQ ID NO: 3 or 4, wherein BC, DE and FG loops as represented by (Z)_(x), (Z)_(y), and (Z)_(z), respectively, comprise BC, DE, and FG loops having the amino acid sequences of SEQ ID NOs: 113, 114, and 115, respectively; SEQ ID NOs: 124, 125 and 126, respectively; SEQ ID NOs: 135, 136 and 137, respectively; SEQ ID NOs: 146, 147 and 148, respectively; SEQ ID NOs: 157, 158 and 159, respectively; SEQ ID NOs: 168, 169 and 170, respectively; SEQ ID NOs: 179, 180 and 181, respectively; SEQ ID NOs: 190, 191 and 192, respectively; SEQ ID NOs: 201, 202 and 203, respectively; SEQ ID NOs: 212, 213 and 214, respectively; SEQ ID NOs: 223, 224 and 225, respectively; SEQ ID NOs: 234, 235, and 236, respectively; SEQ ID NOs: 245, 246 and 247, respectively; SEQ ID NOs: 256, 257 and 258, respectively; SEQ ID NOs: 267, 268 and 269, respectively; SEQ ID NOs: 278, 279 and 280, respectively; SEQ ID NOs: 289, 290 and 291, respectively; SEQ ID NOs: 300, 301 and 302, respectively; SEQ ID NOs: 311, 312 and 313, respectively; SEQ ID NOs: 322, 323 and 324, respectively; SEQ ID NOs: 333, 334 and 335, respectively; SEQ ID NOs: 344, 345 and 346, respectively; SEQ ID NOs: 355, 356 and 357, respectively; SEQ ID NOs: 366, 367 and 368, respectively; SEQ ID NOs: 377, 378 and 379, respectively; SEQ ID NOs: 388, 389 and 390 respectively; SEQ ID NOs: 399, 400 and 401, respectively; SEQ ID NOs: 410, 411 and 412, respectively; SEQ ID NOs: 421, 422 and 423, respectively; SEQ ID NOs: 432, 433 and 434 respectively; SEQ ID NOs: 443, 444 and 445, respectively; SEQ ID NOs: 454, 455 and 456, respectively; SEQ ID NOs: 465, 466 and 467, respectively; SEQ ID NOs: 476, 477 and 478, respectively; SEQ ID NOs: 487, 488 and 489, respectively; SEQ ID NOs: 498, 499 and 500, respectively; SEQ ID NOs: 509, 510 and 511, respectively; SEQ ID NOs: 520, 521 and 522, respectively; SEQ ID NOs: 531, 530 and 531, respectively; SEQ ID NOs: 542, 543 and 544, respectively; SEQ ID NOs: 553, 554 and 555, respectively; or SEQ ID NOs: 564, 565 and 566, respectively. The scaffold regions of such anti-PD-L1 Adnectins may comprise anywhere from 0 to 20, from 0 to 15, from 0 to 10, from 0 to 8, from 0 to 6, from 0 to 5, from 0 to 4, from 0 to 3, from 0 to 2, or from 0 to 1 substitutions, conservative substitutions, deletions or additions relative to the scaffold amino acids residues of SEQ ID NO: 4. Such scaffold modifications may be made, so long as the anti-PD-L1 Adnectin is capable of binding PD-L1 with a desired K_(D).

In certain embodiments, the BC loop of the anti-PD-L1 Adnectin comprises an amino acid sequence selected from the group consisting of: 6, 21, 36, 51, 66, 81, and 97.

In certain embodiments, the DE loop of the anti-PD-L1 Adnectin comprises an amino acid sequence selected from the group consisting of: 7, 22, 37, 52, 67, 82, and 98.

In certain embodiments, the FG loop of the anti-PD-L1 Adnectin comprises an amino acid sequence selected from the group consisting of: 8, 23, 38, 53, 68, 83, and 99.

In certain embodiments, the anti-PD-L1 Adnectin comprises a BC, DE and FG loop amino acid sequence at least 70%, 75%, 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to any one of SEQ ID NOs: 6, 21, 36, 51, 66, 81, and 97; 7, 22, 37, 52, 67, 82, and 98; and 8, 23, 38, 53, 68, 83, and 99, respectively.

In certain embodiments, the anti-PD-L1 Adnectin comprises an amino acid sequence at least 70%, 75%, 80%, 85%, 90%, 95%, 98%, 99%, or 100% identical to any one of SEQ ID NOs: 5, 20, 35, 50, 65, 80, 96, 112, 123, 134, 145, 156, 167, 178, 189, 200, 211, 222, 233, 244, 255, 266, 277, 288, 299, 310, 321, 332, 343, 354, 365, 376, 387, 398, 409, 420, 431, 442, 453, 464, 475, 486, 497, 508, 519, 530, 541, 552 and 563.

In certain embodiments, the anti-PD-L1 Adnectins described herein comprise an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to the non-BC, DE, and FG loop regions of SEQ ID NOs: 5, 20, 35, 50, 65, 80, or 96.

In certain embodiments, the anti-PD-L1 Adnectin comprises an amino acid sequence at least 70%, 75%, 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to any one of SEQ ID NOs: 9-15, 24-30, 39-45, 54-60, 6975, 84-91, 100-107, 116-122, 127-133, 138-144, 150-155, 160-166, 171-177, 182-188, 193-199, 204-210, 215-221, 227-232, 237-243, 248-254, 259-265, 271-276, 291-287, 292-298, 303-309, 314-320, 325-331, 337-342, 347-353, 358-364, 369-375, 380-386, 391-397, 402-408, 413-419, 424-430, 435-441, 446-452, 457-463, 468-474, 479-485, 490-496, 501-507, 512-518, 523-529, 534-540, 545-551, and 556-562. In certain embodiments, the anti-PD-L1 Adnectins described herein comprise an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to the non-BC, DE, and FG loop regions of any one of SEQ ID NOs: 9-15, 24-30, 39-45, 54-60, 6975, 84-91, and 100-107.

In certain embodiments, the anti-PD-L1 Adnectin comprises BC, DE, and FG loops as set forth in SEQ ID NOs: 6, 7, and 8, respectively.

In certain embodiments, the anti-PD-L1 Adnectin comprises BC, DE, and FG loops as set forth in SEQ ID NOs: 21, 22, and 23, respectively.

In certain embodiments, the anti-PD-L1 Adnectin comprises BC, DE, and FG loops as set forth in SEQ ID NOs: 36, 37, and 38, respectively.

In certain embodiments, the anti-PD-L1 Adnectin comprises BC, DE, and FG loops as set forth in SEQ ID NOs: 51, 52, and 53, respectively.

In certain embodiments, the anti-PD-L1 Adnectin comprises BC, DE, and FG loops as set forth in SEQ ID NOs: 66, 67, and 68, respectively.

In certain embodiments, the anti-PD-L1 Adnectin comprises BC, DE, and FG loops as set forth in SEQ ID NOs: 81, 82, and 83, respectively.

In certain embodiments, the anti-PD-L1 Adnectin comprises BC, DE, and FG loops as set forth in SEQ ID NOs: 97, 98, and 99, respectively.

In certain embodiments, BC, DE and/or FG loop amino acid sequences described herein (e.g., SEQ ID NOs: 6, 21, 36, 51, 66, 81, and 97; 7, 22, 37, 52, 67, 82, and 98; and 8, 23, 38, 53, 68, 83, and 99, respectively) are grafted into non-¹⁰Fn3 domain protein scaffolds. For instance, one or more loop amino acid sequences is exchanged for or inserted into one or more CDR loops of an antibody heavy or light chain or fragment thereof. In some embodiments, the protein domain into which one or more amino acid loop sequences are exchanged or inserted includes, but is not limited to, consensus Fn3 domains (Centocor, US), ankyrin repeat proteins (Molecular Partners AG, Zurich Switzerland), domain antibodies (Domantis, Ltd, Cambridge, Mass.), single domain camelid nanobodies (Ablynx, Belgium), lipocalins (e.g., anticalins; Pieris Proteolab AG, Freising, Germany), Avimers (Amgen, Calif.), affibodies (Affibody AG, Sweden), ubiquitin (e.g., affilins; Scil Proteins GmbH, Halle, Germany), protein epitope mimetics (Polyphor Ltd, Allschwil, Switzerland), helical bundle scaffolds (e.g. alphabodies, Complix, Belgium), Fyn SH3 domains (Covagen AG, Switzerland), or atrimers (Anaphor, Inc., CA).

In certain embodiments, the amino acid sequences of the N-terminal and/or C-terminal regions of the polypeptides provided herein may be modified by deletion, substitution or insertion relative to the amino acid sequences of the corresponding regions of the wild-type human ¹⁰Fn3 domain (SEQ ID NO: 1 or 2). The ¹⁰Fn3 domains generally begin with amino acid number 1 of SEQ ID NO: 1. However, domains with amino acid deletions are also encompassed by the invention. Additional sequences may also be added to the N- or C-terminus of a ¹⁰Fn3 domain having the amino acid sequence of SEQ ID NO: 1 or 2. For example, in some embodiments, the N-terminal extension consists of an amino acid sequence selected from the group consisting of: M, MG, and G. In certain embodiments, an MG sequence may be placed at the N-terminus of the ¹⁰Fn3 defined by SEQ ID NO: 1. The M will usually be cleaved off, leaving a G at the N-terminus. In addition, an M, G or MG may also be placed N-terminal to any of the N-terminal extensions shown in Table 3.

In exemplary embodiments, an alternative N-terminal region having from 1-20, 1-15, 1-10, 1-8, 1-5, 1-4, 1-3, 1-2, or 1 amino acids in length can be added to the N-terminal region of SEQ ID NO: 1 or 2 or any adnectin set forth in Table 3. Exemplary alternative N-terminal regions include (represented by the single letter amino acid code) M, MG, G, MGVSDVPRDL (SEQ ID NO: 574) and GVSDVPRDL (SEQ ID NO: 575). Other suitable alternative N-terminal regions, which may be linked, e.g., to the N-terminus of an adnectin core sequence, include, for example, X_(n)SDVPRDL (SEQ ID NO: 576), X_(n)DVPRDL (SEQ ID NO: 577), X_(n)VPRDL (SEQ ID NO: 578), X_(n)PRDL (SEQ ID NO: 579) X_(n)RDL (SEQ ID NO: 580), X_(n)DL (SEQ ID NO: 581), or X_(n)L, wherein n=0, 1 or 2 amino acids, wherein when n=1, X is Met or Gly, and when n=2, X is Met-Gly. When a Met-Gly sequence is added to the N-terminus of a ¹⁰Fn3 domain, the M will usually be cleaved off, leaving a G at the N-terminus. In some embodiments, the alternative N-terminal region comprises the amino acid sequence MASTSG (SEQ ID NO: 582).

In exemplary embodiments, an alternative C-terminal region having from 1-20, 1-15, 1-10, 1-8, 1-5, 1-4, 1-3, 1-2, or 1 amino acids in length can be added to the C-terminal region of SEQ ID NO: 1 or 2 or any adnectin set forth in Table 3. Specific examples of alternative C-terminal region sequences include, for example, polypeptides comprising, consisting essentially of, or consisting of, EIEK (SEQ ID NO: 584), EGSGC (SEQ ID NO: 585), EIEKPCQ (SEQ ID NO: 586), EIEKPSQ (SEQ ID NO: 587), EIEKP (SEQ ID NO: 588), EIEKPS (SEQ ID NO: 589), or EIEKPC (SEQ ID NO: 590). In some embodiments, the alternative C-terminal region comprises EIDK (SEQ ID NO: 591), and in particular embodiments, the alternative C-terminal region is either EIDKPCQ (SEQ ID NO: 592) or EIDKPSQ (SEQ ID NO: 593). Additional suitable alternative C-terminal regions are set forth in SEQ ID NOs: 594-618.

In certain embodiments, an Adnectin is linked to a C-terminal extension sequence that comprises E and D residues, and may be between 8 and 50, 10 and 30, 10 and 20, 5 and 10, and 2 and 4 amino acids in length. In some embodiments, tail sequences include ED-based linkers in which the sequence comprises tandem repeats of ED. In exemplary embodiments, the tail sequence comprises 2-10, 2-7, 2-5, 3-10, 3-7, 3-5, 3, 4 or 5 ED repeats. In certain embodiments, the ED-based tail sequences may also include additional amino acid residues, such as, for example: EI, EID, ES, EC, EGS, and EGC. Such sequences are based, in part, on known Adnectin tail sequences, such as EIDKPSQ (SEQ ID NO: 593), in which residues D and K have been removed. In exemplary embodiments, the ED-based tail comprises an E, I or E1 residues before the ED repeats.

In certain embodiments, the N- or C-terminal extension sequences are linked to the anti-PD-L1 Adnectin sequences with known linker sequences (e.g., SEQ ID NOs: 629-678 in Table 3). In some embodiments, sequences may be placed at the C-terminus of the ¹⁰Fn3 domain to facilitate attachment of a pharmacokinetic moiety. For example, a cysteine containing linker such as GSGC (SEQ ID NO: 638) may be added to the C-terminus to facilitate site directed PEGylation on the cysteine residue.

In certain embodiments, an alternative C-terminal moiety, which can be linked to the C-terminal amino acids RT (i.e., amino acid 94) comprises the amino acids P_(m)X_(n), wherein P is proline, X is any amino acid, m is an integer that is at least 1 and n is 0 or an interger that is at least 1. In certain embodiments, the alternative C-terminal moiety comprises the amino acids PC. In certain embodiments, the alternative C-terminal moiety comprises the amino acids PI, PC, PID, PIE, PIDK (SEQ ID NO: 605), PIEK (SEQ ID NO: 606), PIDKP (SEQ ID NO: 607), PIEKP (SEQ ID NO: 608), PIDKPS (SEQ ID NO: 609), PIEKPS (SEQ ID NO: 610), PIDKPC (SEQ ID NO: 611), PIEKPC (SEQ ID NO: 612), PIDKPSQ (SEQ ID NO: 613), PIEKPSQ (SEQ ID NO: 614), PIDKPCQ (SEQ ID NO: 615), PIEKPCQ (SEQ ID NO: 616), PHHHHHH (SEQ ID NO: 617), and PCHHHHHH (SEQ ID NO: 618). Exemplary anti-PD-L1 Adnectins having PC at their C-terminus are provided in the Examples and Table 3.

In certain embodiments, the Adnectins described herein have a 6× his tail (SEQ ID NO: 619).

In certain embodiments, the fibronectin based scaffold proteins comprise a ¹⁰Fn3 domain having both an alternative N-terminal region sequence and an alternative C-terminal region sequence, and optionally a 6× his tail.

II. BIOLOGICAL PROPERTIES OF ANTI-PD-L1 ADNECTINS

Provided herein are adnectins that bind to human PD-L1 with a KD of 10 nM, 1 nM, 0.5 nM, 0.1 nM or less, as determined, e.g., by SPR (Biacore) and exhibit one or more of the following properties:

-   1. Inhibition of the interaction between human PD-L1 and human PD-1     by at least 50%, 70%, 80%, 90% or more, as determined, e.g., by flow     cytometry, e.g., using a human PD-1Fc protein and human PD-L1     positive cells, such as L2987 cells; -   2. Inhibition of the binding of human CD80 (B7-1) to human PD-L1 by     at least 50%, 70%, 80%, 90% or more, as determined, e.g., in an     ELISA assay or by SPR (Biacore); -   3. Inhibition of the binding of the anti-PD-L1 antibody 12A4     (described, e.g., in U.S. Pat. No. 7,943,743) to human PD-L1 by at     least 50%, 70%, 80%, 90% or more, as determined, e.g., in an ELISA     assay or by SPR (Biacore); and -   4. Inhibit cell proliferation in a mixed lymphocyte reaction (MLR).

In certain embodiments, an anti-PD-L1 adnectin binds to human PD-L1 with a KD of 1 nM or less and exhibits each one of properties 1-4. In certain embodiments, an anti-PD-L1 adnectin binds to human PD-L1 with a KD of 0.1 nM or less and exhibits each one of properties 1-4.

Provided herein are adnectins that comprise an amino acid sequence that is at least 70%, 80%, 90%, 95%, 97%, 98% or 99% identical to an anti-PD-L1 adnectin described herein or a portion thereof (e.g., the BC, DE and FG loops), bind to human PD-L1 with a KD of 10 nM, 1 nM, 0.5 nM, 0.1 nM or less, as determined, e.g., by SPR (Biacore) and exhibit one or more of the following properties:

-   1. Inhibition of the interaction between human PD-L1 and human PD-1     by at least 50%, 70%, 80%, 90% or more, as determined, e.g., by flow     cytometry, e.g., using a human PD-1Fc protein and human PD-L1     positive cells, such as L2987 cells; -   2. Inhibition of the binding of human CD80 (B7-1) to human PD-L1 by     at least 50%, 70%, 80%, 90% or more, as determined, e.g., in an     ELISA assay or by SPR (Biacore); -   3. Inhibition of the binding of the anti-PD-L1 antibody 12A4 to     human PD-L1 by at least 50%, 70%, 80%, 90% or more, as determined,     e.g., in an ELISA assay or by SPR (Biacore); and -   4. Inhibit cell proliferation in a mixed lymphocyte reaction (MLR).

In certain embodiments, an anti-PD-L1 adnectin comprises an amino acid sequence that is at least 70%, 80%, 90%, 95%, 97%, 98% or 99% identical to an anti-PD-L1 adnectin described herein or a portion thereof (e.g., the BC, DE and FG loops), binds to human PD-L1 with a KD of 1 nM or less and exhibits each one of properties 1-4. In certain embodiments, an anti-PD-L1 adnectin comprises an amino acid sequence that is at least 70%, 80%, 90%, 95%, 97%, 98% or 99% identical to an anti-PD-L1 adnectin described herein or a portion thereof (e.g., the BC, DE and FG loops), binds to human PD-L1 with a KD of 0.1 nM or less and exhibits each one of properties 1-4.

In certain embodiments, the anti-PD-L1 Adnectins compete (e.g., cross-compete) for binding to PD-L1 with the particular anti-PD-L1 Adnectins described herein. Such competing Adnectins can be identified based on their ability to competitively inhibit binding to PD-L1 of Adnectins described herein in standard PD-L1 binding assays. For example, standard ELISA assays can be used in which a recombinant PD-L1 protein is immobilized on the plate, one of the Adnectins is fluorescently labeled and the ability of non-labeled Adnectins to compete off the binding of the labeled Adnectin is evaluated.

In certain embodiments, a competitive ELISA format can be performed to determine whether two anti-PD-L1 Adnectins bind overlapping Adnectin binding sites on PD-L1. In one format, Adnectin #1 is coated on a plate, which is then blocked and washed. To this plate is added either PD-L1 alone, or PD-L1 pre-incubated with a saturating concentration of Adnectin #2. After a suitable incubation period, the plate is washed and probed with a polyclonal anti-PD-L1 antibody, such as a biotinylated anti-PD-L1 polyclonal antibody, followed by detection with streptavidin-HRP conjugate and standard tetramethylbenzidine development procedures. If the OD signal is the same with or without preincubation with Adnectin #2, then the two Adnectins bind independently of one another, and their Adnectin binding sites do not overlap. If, however, the OD signal for wells that received PD-L1/Adnectin #2 mixtures is lower than for those that received PD-L1 alone, then binding of Adnectin #2 is confirmed to block binding of Adnectin #1 to PD-L1.

Alternatively, a similar experiment is conducted by surface plasmon resonance (SPR, e.g., BIAcore). Adnectin #1 is immobilized on an SPR chip surface, followed by injections of either PD-L1 alone or PD-L1 pre-incubated with a saturating concentration of Adnectin #2. If the binding signal for PD-L1/Adnectin #2 mixtures is the same or higher than that of PD-L1 alone, then the two Adnectins bind independently of one another, and their Adnectin binding sites do not overlap. If, however, the binding signal for PD-L1/Adnectin #2 mixtures is lower than the binding signal for PD-L1 alone, then binding of Adnectin #2 is confirmed to block binding of Adnectin #1 to PD-L1. A feature of these experiments is the use of saturating concentrations of Adnectin #2. If PD-L1 is not saturated with Adnectin #2, then the conclusions above do not hold. Similar experiments can be used to determine if any two PD-L1 binding proteins bind to overlapping Adnectin binding sites.

Both assays exemplified above may also be performed in the reverse order where Adnectin #2 is immobilized and PD-L1-Adnectin #1 are added to the plate. Alternatively, Adnectin #1 and/or #2 can be replaced with a monoclonal antibody and/or soluble receptor-Fc fusion protein.

In certain embodiments, competition can be determined using a HTRF sandwich assay.

In certain embodiments, the competing Adnectin is an Adnectin that binds to the same Adnectin binding site on PD-L1 as a particular anti-PD-L1 Adnectin described herein. Standard mapping techniques, such as protease mapping, mutational analysis, HDX-MS, x-ray crystallography and 2-dimensional nuclear magnetic resonance, can be used to determine whether an Adnectin binds to the same Adnectin binding site or epitope as a reference Adnectin (see, e.g., Epitope Mapping Protocols in Methods in Molecular Biology, Vol. 66, G. E. Morris, Ed. (1996)). An epitope is defined by the method used to locate it. For example, in certain embodiments, a PD-L1 adnectin or antibody binds to the same epitope as that of one of the PD-L1 adnectins described herein, as determined by HDX-MS or as determined by X-ray crystallography.

Candidate competing anti-PD-L1 Adnectins can inhibit the binding of anti-PD-L1 Adnectins described herein to PD-L1 by at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, at least 98%, or at least 99% and/or their binding is inhibited by at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, at least 98%, or at least 99% by anti-PD-L1 Adnectins. The % competition can be determined using the methods described above.

Provided herein are adnectins that bind to human PD-L1 with a KD of 10 nM, 1 nM, 0.5 nM, 0.1 nM or less, as determined, e.g., by SPR (Biacore) and exhibit one or more of the following properties:

-   1. Inhibition of the interaction between human PD-L1 and human PD-1     by at least 50%, 70%, 80%, 90% or more, as determined, e.g., by flow     cytometry, e.g., using a human PD-1Fc protein and human PD-L1     positive cells, such as L2987 cells; -   2. Inhibition of the binding of human CD80 (B7-1) to human PD-L1 by     at least 50%, 70%, 80%, 90% or more, as determined, e.g., in an     ELISA assay or by SPR (Biacore); -   3. Inhibition of the binding of the anti-PD-L1 antibody 12A4 to     human PD-L1 by at least 50%, 70%, 80%, 90% or more, as determined,     e.g., in an ELISA assay or by SPR (Biacore); -   4. Inhibit cell proliferation in a mixed lymphocyte reaction (MLR);     and -   5. Compete with an anti-PD-L1 antibody described herein for binding     to human PD-L1.

In certain embodiments, an anti-PD-L1 adnectin binds to human PD-L1 with a KD of 1 nM or less and exhibits each one of properties 1-5. In certain embodiments, an anti-PD-L1 adnectin binds to human PD-L1 with a KD of 0.1 nM or less and exhibits each one of properties 1-5.

Provided herein are adnectins that comprise an amino acid sequence that is at least 70%, 80%, 90%, 95%, 97%, 98% or 99% identical to an anti-PD-L1 adnectin described herein or a portion thereof (e.g., the BC, DE and FG loops), bind to human PD-L1 with a KD of 10 nM, 1 nM, 0.5 nM, 0.1 nM or less, as determined, e.g., by SPR (Biacore) and exhibit one or more of the following properties:

-   1. Inhibition of the interaction between human PD-L1 and human PD-1     by at least 50%, 70%, 80%, 90% or more, as determined, e.g., by flow     cytometry, e.g., using a human PD-1Fc protein and human PD-L1     positive cells, such as L2987 cells; -   2. Inhibition of the binding of human CD80 (B7-1) to human PD-L1 by     at least 50%, 70%, 80%, 90% or more, as determined, e.g., in an     ELISA assay or by SPR (Biacore); -   3. Inhibition of the binding of the anti-PD-L1 antibody 12A4 to     human PD-L1 by at least 50%, 70%, 80%, 90% or more, as determined,     e.g., in an ELISA assay or by SPR (Biacore); -   4. Inhibit cell proliferation in a mixed lymphocyte reaction (MLR);     and -   5. Compete with an anti-PD-L1 antibody described herein for binding     to human PD-L1.

In certain embodiments, an anti-PD-L1 adnectin comprises an amino acid sequence that is at least 70%, 80%, 90%, 95%, 97%, 98% or 99% identical to an anti-PD-L1 adnectin described herein or a portion thereof (e.g., the BC, DE and FG loops), binds to human PD-L1 with a KD of 1 nM or less and exhibits each one of properties 1-5. In certain embodiments, an anti-PD-L1 adnectin comprises an amino acid sequence that is at least 70%, 80%, 90%, 95%, 97%, 98% or 99% identical to an anti-PD-L1 adnectin described herein or a portion thereof (e.g., the BC, DE and FG loops), binds to human PD-L1 with a KD of 0.1 nM or less and exhibits each one of properties 1-5.

III. FUSIONS, INCLUDING PHARMACOKINETIC MOIETIES

In certain embodiments, the anti-PD-L1 Adnectins desirably have a short half-life, for example, when used in PET imaging. In certain embodiments, an anti-PD-L1 adnectin has a half-life in blood or serum of 30 minutes to 3 hours, 30 minutes to 120 minutes, 60 minutes to 120 minutes, or 80 minutes to 100 minutes. In certain embodiments, the half-life of a PD-L1 Adnectin is similar to that of the label that is attached to it, e.g., ¹⁸F.

The anti-PD-L1 Adnectins described herein may comprise a pharmacokinetic (PK) moiety. Improved pharmacokinetics may be assessed according to the perceived therapeutic need. The anti-PD-L1 Adnectin may be attached to a moiety that reduces the clearance rate of the polypeptide in a human by greater than two-fold, greater than three-fold, greater than four-fold or greater than five-fold relative to the unmodified anti-PD-L1 Adnectin. Other measures of improved pharmacokinetics may include serum half-life, which is often divided into an alpha phase and a beta phase. Either or both phases may be improved significantly by addition of an appropriate moiety. For example, the PK moiety may increase the serum half-life of the polypeptide by more than 10%, 20%, 50%, 2 fold, 3 fold or 5 fold relative to the Fn3 domain (or Adnectin) alone.

Moieties that slow clearance of a protein from the blood, herein referred to as “PK moieties”, include polyoxyalkylene moieties (e.g., polyethylene glycol), sugars (e.g., sialic acid), and well-tolerated protein moieties (e.g., Fc and fragments and variants thereof, transferrin, or serum albumin). Other PK moieties that can be used in the invention include those described in Kontermann et al., (Current Opinion in Biotechnology 2011; 22:868-76), herein incorporated by reference. Such PK moieties include, but are not limited to PAS fusions (i.e., recombinant PEG mimetics based on the three amino acids proline, alanine, and serine), carbohydrate conjugates (e.g., hydroxyethyl starch (HES)), glycosylation, polysialic acid conjugates, and fatty acid conjugates.

IV. NUCLEIC ACID-PROTEIN FUSION TECHNOLOGY

In one aspect, the invention provides an Adnectin comprising fibronectin type III domains that binds PD-L1. One way to rapidly make and test Fn3 domains with specific binding properties is the nucleic acid-protein fusion technology of Adnexus, a Bristol-Myers Squibb R&D Company. This disclosure utilizes the in vitro expression and tagging technology, termed ‘PROfusion’ which exploits nucleic acid-protein fusions (RNA- and DNA-protein fusions) to identify novel polypeptides and amino acid motifs that are important for binding to proteins. Nucleic acid-protein fusion technology is a technology that covalently couples a protein to its encoding genetic information. For a detailed description of the RNA-protein fusion technology and fibronectin-based scaffold protein library screening methods see Szostak et al., U.S. Pat. Nos. 6,258,558, 6,261,804, 6,214,553, 6,281,344, 6,207,446, 6,518,018 and 6,818,418; Roberts et al., Proc. Natl. Acad. Sci., 1997; 94:12297-12302; and Kurz et al., Molecules, 2000; 5:1259-64, all of which are herein incorporated by reference.

V. VECTORS AND POLYNUCLEOTIDES

Also included in the present disclosure are nucleic acid sequences encoding any of the proteins described herein. As appreciated by those skilled in the art, because of third base degeneracy, almost every amino acid can be represented by more than one triplet codon in a coding nucleotide sequence. In addition, minor base pair changes may result in a conservative substitution in the amino acid sequence encoded but are not expected to substantially alter the biological activity of the gene product. Therefore, a nucleic acid sequence encoding a protein described herein may be modified slightly in sequence and yet still encode its respective gene product. Certain exemplary nucleic acids encoding the anti-PD-L1 Adnectins and their fusions described herein include nucleic acids having the sequences set forth in SEQ ID NOs: 16-19, 31-34, 46-49, 61-64, 76-79, 92-95, and 108-111.

Also contemplated are nucleic acid sequences that are at least 50%, such as at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NOs: 16-19, 31-34, 46-49, 61-64, 76-79, 92-95, and 108-111, and encode a protein that binds to PD-L1. In some embodiments, nucleotide substitutions are introduced so as not to alter the resulting translated amino acid sequence.

Nucleic acids encoding any of the various proteins or polypeptides described herein may be synthesized chemically. Codon usage may be selected so as to improve expression in a cell. Such codon usage will depend on the cell type selected. Specialized codon usage patterns have been developed for E. coli and other bacteria, as well as mammalian cells, plant cells, yeast cells and insect cells. See for example: Mayfield et al., Proc. Natl. Acad. Sci. USA, 100(2):438-442 (Jan. 21, 2003); Sinclair et al., Protein Expr. Purif., 26(I):96-105 (October 2002); Connell, N. D., Curr. Opin. Biotechnol., 12(5):446-449 (October 2001); Makrides et al., Microbiol. Rev., 60(3):512-538 (September 1996); and Sharp et al., Yeast, 7(7):657-678 (October 1991).

General techniques for nucleic acid manipulation are described in, for example, Sambrook et al., Molecular Cloning: A Laboratory Manual, 2nd Edition, Vols. 1-3, Cold Spring Harbor Laboratory Press (1989), or Ausubel, F. et al., Current Protocols in Molecular Biology, Green Publishing and Wiley-Interscience, New York (1987) and periodic updates, herein incorporated by reference. Generally, the DNA encoding the polypeptide is operably linked to suitable transcriptional or translational regulatory elements derived from mammalian, viral, or insect genes. Such regulatory elements include a transcriptional promoter, an optional operator sequence to control transcription, a sequence encoding suitable mRNA ribosomal binding site, and sequences that control the termination of transcription and translation. The ability to replicate in a host, usually conferred by an origin of replication, and a selection gene to facilitate recognition of transformants is additionally incorporated.

The proteins described herein may be produced recombinantly not only directly, but also as a fusion polypeptide with a heterologous polypeptide, which is preferably a signal sequence or other polypeptide having a specific cleavage site at the N-terminus of the mature protein or polypeptide. The heterologous signal sequence selected preferably is one that is recognized and processed (i.e., cleaved by a signal peptidase) by the host cell. An exemplary N-terminal leader sequence for production of polypeptides in a mammalian system is: METDTLLLWVLLLWVPGSTG (SEQ ID NO: 583), which is removed by the host cell following expression.

For prokaryotic host cells that do not recognize and process a native signal sequence, the signal sequence is substituted by a prokaryotic signal sequence selected, for example, from the group of the alkaline phosphatase, penicillinase, 1 pp, or heat-stable enterotoxin II leaders.

For yeast secretion the native signal sequence may be substituted by, e.g., a yeast invertase leader, a factor leader (including Saccharomyces and Kluyveromyces alpha-factor leaders), or acid phosphatase leader, the C. albicans glucoamylase leader, or the signal sequence described in U.S. Pat. No. 5,631,144. In mammalian cell expression, mammalian signal sequences as well as viral secretory leaders, for example, the herpes simplex gD signal, are available. The DNA for such precursor regions may be ligated in reading frame to DNA encoding the protein.

Both expression and cloning vectors contain a nucleic acid sequence that enables the vector to replicate in one or more selected host cells. Generally, in cloning vectors this sequence is one that enables the vector to replicate independently of the host chromosomal DNA, and includes origins of replication or autonomously replicating sequences. Such sequences are well known for a variety of bacteria, yeast, and viruses. The origin of replication from the plasmid pBR322 is suitable for most Gram-negative bacteria, the 2 micron plasmid origin is suitable for yeast, and various viral origins (SV40, polyoma, adenovirus, VSV or BPV) are useful for cloning vectors in mammalian cells. Generally, the origin of replication component is not needed for mammalian expression vectors (the SV40 origin may typically be used only because it contains the early promoter).

Expression and cloning vectors may contain a selection gene, also termed a selectable marker. Typical selection genes encode proteins that (a) confer resistance to antibiotics or other toxins, e.g., ampicillin, neomycin, methotrexate, or tracycline, (b) complement auxotrophic deficiencies, or (c) supply critical nutrients not available from complex media, e.g., the gene encoding D-alanine racemase for Bacilli.

Expression and cloning vectors usually contain a promoter that is recognized by the host organism and is operably linked to the nucleic acid encoding the protein described herein, e.g., a fibronectin-based scaffold protein. Promoters suitable for use with prokaryotic hosts include the phoA promoter, beta-lactamase and lactose promoter systems, alkaline phosphatase, a tryptophan (trp) promoter system, and hybrid promoters such as the tan promoter. However, other known bacterial promoters are suitable. Promoters for use in bacterial systems also will contain a Shine-Dalgarno (S.D.) sequence operably linked to the DNA encoding the protein described herein. Promoter sequences are known for eukaryotes. Virtually all eukaryotic genes have an AT-rich region located approximately 25 to 30 bases upstream from the site where transcription is initiated. Another sequence found 70 to 80 bases upstream from the start of transcription of many genes is a CNCAAT region where N may be any nucleotide. At the 3′ end of most eukaryotic genes is an AATAAA sequence that may be the signal for addition of the poly A tail to the 3′ end of the coding sequence. All of these sequences are suitably inserted into eukaryotic expression vectors.

Examples of suitable promoting sequences for use with yeast hosts include the promoters for 3-phosphoglycerate kinase or other glycolytic enzymes, such as enolase, glyceraldehyde-3-phosphate dehydrogenase, hexokinase, pyruvate decarboxylase, phosphofructokinase, glucose-6-phosphate isomerase, 3-phosphoglycerate mutase, pyruvate kinase, triosephosphate isomerase, phosphoglucose isomerase, and glucokinase.

Transcription from vectors in mammalian host cells can be controlled, for example, by promoters obtained from the genomes of viruses such as polyoma virus, fowlpox virus, adenovirus (such as Adenovirus 2), bovine papilloma virus, avian sarcoma virus, cytomegalovirus, a retrovirus, hepatitis-B virus and most preferably Simian Virus 40 (SV40), from heterologous mammalian promoters, e.g., the actin promoter or an immunoglobulin promoter, from heat-shock promoters, provided such promoters are compatible with the host cell systems.

Transcription of a DNA encoding protein described herein by higher eukaryotes is often increased by inserting an enhancer sequence into the vector. Many enhancer sequences are now known from mammalian genes (globin, elastase, albumin, α-fetoprotein, and insulin). Typically, however, one will use an enhancer from a eukaryotic cell virus. Examples include the SV40 enhancer on the late side of the replication origin (bp 100-270), the cytomegalovirus early promoter enhancer, the polyoma enhancer on the late side of the replication origin, and adenovirus enhancers. See also Yaniv, Nature, 297:17-18 (1982) on enhancing elements for activation of eukaryotic promoters. The enhancer may be spliced into the vector at a position 5′ or 3′ to the peptide-encoding sequence, but is preferably located at a site 5′ from the promoter.

Expression vectors used in eukaryotic host cells (e.g., yeast, fungi, insect, plant, animal, human, or nucleated cells from other multicellular organisms) will also contain sequences necessary for the termination of transcription and for stabilizing the mRNA. Such sequences are commonly available from the 5′ and, occasionally 3′, untranslated regions of eukaryotic or viral DNAs or cDNAs. These regions contain nucleotide segments transcribed as polyadenylated fragments in the untranslated portion of mRNA encoding the protein described herein. One useful transcription termination component is the bovine growth hormone polyadenylation region. See WO 94/11026 and the expression vector disclosed therein.

The recombinant DNA can also include any type of protein tag sequence that may be useful for purifying the protein. Examples of protein tags include, but are not limited to, a histidine tag, a FLAG tag, a myc tag, an HA tag, or a GST tag. Appropriate cloning and expression vectors for use with bacterial, fungal, yeast, and mammalian cellular hosts can be found in Cloning Vectors: A Laboratory Manual, (Elsevier, New York (1985)), the relevant disclosure of which is hereby incorporated by reference.

The expression construct is introduced into the host cell using a method appropriate to the host cell, as will be apparent to one of skill in the art. A variety of methods for introducing nucleic acids into host cells are known in the art, including, but not limited to, electroporation; transfection employing calcium chloride, rubidium chloride, calcium phosphate, DEAE-dextran, or other substances; microprojectile bombardment; lipofection; and infection (where the vector is an infectious agent).

Suitable host cells include prokaryotes, yeast, mammalian cells, or bacterial cells. Suitable bacteria include gram negative or gram positive organisms, for example, E. coli or Bacillus spp. Yeast, preferably from the Saccharomyces species, such as S. cerevisiae, may also be used for production of polypeptides. Various mammalian or insect cell culture systems can also be employed to express recombinant proteins. Baculovirus systems for production of heterologous proteins in insect cells are reviewed by Luckow et al. (Bio/Technology, 6:47 (1988)). Examples of suitable mammalian host cell lines include endothelial cells, COS-7 monkey kidney cells, CV-1, L cells, C127, 3T3, Chinese hamster ovary (CHO), human embryonic kidney cells, HeLa, 293, 293T, and BHK cell lines. Purified polypeptides are prepared by culturing suitable host/vector systems to express the recombinant proteins. For many applications, the small size of many of the polypeptides described herein would make expression in E. coli as the preferred method for expression. The protein is then purified from culture media or cell extracts.

VI. PROTEIN PRODUCTION

Also described herein are cell lines that express an anti-PD-L1 Adnectin or fusion polypeptide thereof. Creation and isolation of cell lines producing an anti-PD-L1 Adnectin can be accomplished using standard techniques known in the art, such as those described herein.

Host cells are transformed with the herein-described expression or cloning vectors for protein production and cultured in conventional nutrient media modified as appropriate for inducing promoters, selecting transformants, or amplifying the genes encoding the desired sequences.

Adnectins of the present invention can also be obtained in aglycosylated form by producing the Adnectins in, e.g., prokaryotic cells (e.g., E. coli). Notably, aglycosylated forms of the Adnectins described herein exhibit the same affinity, potency, and mechanism of action as glycosylated Adnectins when tested in vitro.

The host cells used to produce the proteins of this invention may be cultured in a variety of media. Commercially available media such as Ham's F10 (Sigma), Minimal Essential Medium ((MEM), (Sigma), RPMI-1640 (Sigma), and Dulbecco's Modified Eagle's Medium ((DMEM), Sigma)) are suitable for culturing the host cells. In addition, many of the media described in Ham et al., Meth. Enzymol., 58:44 (1979), Barites et al., Anal. Biochem., 102:255 (1980), U.S. Pat. Nos. 4,767,704, 4,657,866, 4,927,762, 4,560,655, 5,122,469, 6,048,728, 5,672,502, or RE 30,985 may be used as culture media for the host cells. Any of these media may be supplemented as necessary with hormones and/or other growth factors (such as insulin, transferrin, or epidermal growth factor), salts (such as sodium chloride, calcium, magnesium, and phosphate), buffers (such as HEPES), nucleotides (such as adenosine and thymidine), antibiotics (such as Gentamycin drug), trace elements (defined as inorganic compounds usually present at final concentrations in the micromolar range), and glucose or an equivalent energy source. Any other necessary supplements may also be included at appropriate concentrations that would be known to those skilled in the art. The culture conditions, such as temperature, pH, and the like, are those previously used with the host cell selected for expression, and will be apparent to the ordinarily skilled artisan.

Proteins described herein can also be produced using cell-free translation systems. For such purposes the nucleic acids encoding the polypeptide must be modified to allow in vitro transcription to produce mRNA and to allow cell-free translation of the mRNA in the particular cell-free system being utilized (eukaryotic such as a mammalian or yeast cell-free translation system or prokaryotic such as a bacterial cell-free translation system).

Proteins described herein can also be produced by chemical synthesis (e.g., by the methods described in Solid Phase Peptide Synthesis, 2nd Edition, The Pierce Chemical Co., Rockford, Ill. (1984)). Modifications to the protein can also be produced by chemical synthesis.

The proteins of the present invention can be purified by isolation/purification methods for proteins generally known in the field of protein chemistry. Non-limiting examples include extraction, recrystallization, salting out (e.g., with ammonium sulfate or sodium sulfate), centrifugation, dialysis, ultrafiltration, adsorption chromatography, ion exchange chromatography, hydrophobic chromatography, normal phase chromatography, reversed-phase chromatography, get filtration, gel permeation chromatography, affinity chromatography, electrophoresis, countercurrent distribution or any combinations of these. After purification, polypeptides may be exchanged into different buffers and/or concentrated by any of a variety of methods known to the art, including, but not limited to, filtration and dialysis.

The purified polypeptide is preferably at least 85% pure, or preferably at least 95% pure, and most preferably at least 98% pure. Regardless of the exact numerical value of the purity, the polypeptide is sufficiently pure for use as a pharmaceutical product.

High Throughput Protein Production (HTPP)

Selected binders cloned into the PET9d vector upstream of a HIS₆tag and are transformed into E. coli BL21 DE3 plysS cells and inoculated in 5 ml LB medium containing 50 μg/mL kanamycin in a 24-well format and grown at 37° C. overnight. Fresh 5 ml LB medium (50 μg/mL kanamycin) cultures are prepared for inducible expression by aspiration of 200 μl from the overnight culture and dispensing it into the appropriate well. The cultures are grown at 37° C. until A₆₀₀ 0.6-0.9. After induction with 1 mM isopropyl-β-thiogalactoside (IPTG), the culture is expressed for 6 hours at 30° C. and harvested by centrifugation for 10 minutes at 2750 g at 4° C.

Cell pellets (in 24-well format) are lysed by resuspension in 450 μl of Lysis buffer (50 mM NaH₂PO₄, 0.5 M NaCl, 1× Complete™ Protease Inhibitor Cocktail-EDTA free (Roche), 1 mM PMSF, 10 mM CHAPS, 40 mM imidazole, 1 mg/ml lysozyme, 30 μg/ml DNAse, 2 μg/ml aprotonin, pH 8.0) and shaken at room temperature for 1-3 hours. Lysates are cleared and re-racked into a 96-well format by transfer into a 96-well Whatman GF/D Unifilter fitted with a 96-well, 1.2 ml catch plate and filtered by positive pressure. The cleared lysates are transferred to a 96-well Nickel or Cobalt-Chelating Plate that had been equilibrated with equilibration buffer (50 mM NaH₂PO₄, 0.5 M NaCl, 40 mM imidazole, pH 8.0) and are incubated for 5 min. Unbound material is removed by positive pressure. The resin is washed twice with 0.3 ml/well with Wash buffer #1 (50 mM NaH₂PO₄, 0.5 M NaCl, 5 mM CHAPS, 40 mM imidazole, pH 8.0). Each wash is removed by positive pressure. Prior to elution, each well is washed with 50 μl Elution buffer (PBS+20 mM EDTA), incubated for 5 min, and this wash is discarded by positive pressure. Protein is eluted by applying an additional 100 μl of Elution buffer to each well. After a 30 minute incubation at room temperature, the plate(s) are centrifuged for 5 minutes at 200 g and eluted protein collected in 96-well catch plates containing 5 μl of 0.5 M MgCl₂ added to the bottom of elution catch plate prior to elution. Eluted protein is quantified using a total protein assay with wild-type ¹⁰Fn3 domain as the protein standard.

Midscale Expression and Purification of Insoluble Fibronectin-Based Scaffold Protein Binders

For expression of insoluble clones, the clone(s), followed by the HIS₆tag, are cloned into a pET9d (EMD Bioscience, San Diego, Calif.) vector and are expressed in E. coli HMS174 cells. Twenty ml of an inoculum culture (generated from a single plated colony) is used to inoculate 1 liter of LB medium containing 50 μg/ml carbenicillin and 34 μg/ml chloramphenicol. The culture is grown at 37° C. until A₆₀₀ 0.6-1.0. After induction with 1 mM isopropyl-β-thiogalactoside (IPTG) the culture is grown for 4 hours at 30° C. and is harvested by centrifugation for 30 minutes at >10,000 g at 4° C. Cell pellets are frozen at −80° C. The cell pellet is resuspended in 25 ml of lysis buffer (20 mM aH2PO₄, 0.5 M NaCl, 1× Complete Protease Inhibitor Cocktail-EDTA free (Roche), ImM PMSF, pH 7.4) using an ULTRA-TURRAX® homogenizer (IKA works) on ice. Cell lysis is achieved by high pressure homogenization (>18,000 psi) using a Model M-1 10S MICROFLUIDIZER® (Microfluidics). The insoluble fraction is separated by centrifugation for 30 minutes at 23,300 g at 4° C. The insoluble pellet recovered from centrifugation of the lysate is washed with 20 mM sodiumphosphate/500 mM NaCl, pH7.4. The pellet is resolubilized in 6.0M guanidine hydrochloride in 20 mM sodium phosphate/500M NaCl pH 7.4 with sonication followed by incubation at 37 degrees for 1-2 hours. The resolubilized pellet is filtered to 0.45 μm and loaded onto a Histrap column equilibrated with the 20 mM sodium phosphate/500 M NaCl/6.0 M guanidine pH 7.4 buffer. After loading, the column is washed for an additional 25 CV with the same buffer. Bound protein is eluted with 50 mM Imidazole in 20 mM sodium phosphate/500 mM NaCl/6.0 M guan-HCl pH7.4. The purified protein is refolded by dialysis against 50 mM sodium acetate/150 mM NaCl pH 4.5.

Midscale Expression and Purification of Soluble Fibronectin-Base Scaffold Protein Binders

For expression of soluble clones, the clone(s), followed by the HIS₆tag, are cloned into a pET9d (EMD Bioscience, San Diego, Calif.) vector and expressed in E. coli HMS174 cells. Twenty ml of an inoculum culture (generated from a single plated colony) is used to inoculate 1 liter of LB medium containing 50 μg/ml carbenicillin and 34 μg/ml chloramphenicol. The culture is grown at 37° C. until A₆₀₀ 0.6-1.0. After induction with 1 mM isopropyl-β-thiogalactoside (IPTG), the culture is grown for 4 hours at 30° C. and harvested by centrifugation for 30 minutes at >10,000 g at 4° C. Cell pellets are frozen at −80° C. The cell pellet is resuspended in 25 ml of lysis buffer (20 mM NaH₂PO₄, 0.5 M NaCl, 1× Complete Protease Inhibitor Cocktail-EDTA free (Roche), ImM PMSF, pH 7.4) using an ULTRA-TURRAX® homogenizer (IKA works) on ice. Cell lysis is achieved by high pressure homogenization (>18,000 psi) using a Model M-1 10S MICROFLUIDIZER® (Microfluidics). The soluble fraction is separated by centrifugation for 30 minutes at 23,300 g at 4° C. The supernatant is clarified via 0.45 μm filter. The clarified lysate is loaded onto a Histrap column (GE) pre-equilibrated with the 20 mM sodium phosphate/500M NaCl pH 7.4. The column is then washed with 25 column volumes of the same buffer, followed by 20 column volumes of 20 mM sodium phosphate/500 M NaCl/25 mM Imidazole, pH 7.4 and then 35 column volumes of 20 mM sodium phosphate/500 M NaCl/40 mM Imidazole, pH 7.4. Protein is eluted with 15 column volumes of 20 mM sodium phosphate/500 M NaCl/500 mM Imidazole, pH 7.4, fractions are pooled based on absorbance at A₂so and dialyzed against 1×PBS, 50 mM Tris, 150 mM NaCl; pH 8.5 or 50 mM NaOAc; 150 mM NaCl; pH4.5. Any precipitate is removed by filtering at 0.22 μm.

VII. COMPOSITIONS

The present invention further provides compositions, such as pharmaceutical compositions and radiopharmaceutical compositions, comprising an anti-PD-L1 Adnectin or fusion proteins thereof described herein, wherein the composition is essentially endotoxin free, or at least contain no more than acceptable levels of endotoxins as determined by the appropriate regulatory agency (e.g., FDA).

Methods well known in the art for making compositions are found, for example, in “Remington: The Science and Practice of Pharmacy” (20th ed., ed. A. R. Gennaro AR., 2000, Lippincott Williams & Wilkins, Philadelphia, Pa.). Compositions for parenteral administration may, for example, contain excipients, sterile water, saline, polyalkylene glycols such as polyethylene glycol, oils of vegetable origin, or hydrogenated napthalenes. Biocompatible, biodegradable lactide polymer, lactide/glycolide copolymer, or polyoxyethylene-polyoxypropylene copolymers may be used to control the release of the compounds. Nanoparticulate compositions (e.g., biodegradable nanoparticles, solid lipid nanoparticles, liposomes) may be used to control the biodistribution of the compounds. Other potentially useful parenteral delivery systems include ethylene-vinyl acetate copolymer particles, osmotic pumps, implantable infusion systems, and liposomes. The concentration of the compound in the composition varies depending upon a number of factors, including the dosage of the drug to be administered, the route of administration, and the purpose of the composition (e.g., prophylactic, therapeutic, diagnostic).

Acceptable carriers, excipients, or stabilizers are nontoxic to recipients at the dosages and concentrations employed, and include buffers such as phosphate, citrate, and other organic acids; antioxidants including ascorbic acid and methionine; preservatives (such as octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride; benzalkonium chloride, benzethonium chloride; phenol, butyl or benzyl alcohol; alkyl parabens such as methyl or propyl paraben; catechol; resorcinol; cyclohexanol; 3-pentanol; and m-cresol); low molecular weight (less than about 10 residues) polypeptides; proteins, such as serum albumin, gelatin, or immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, histidine, arginine, or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrans; chelating agents such as EDTA; sugars such as sucrose, mannitol, trehalose or sorbitol; salt-forming counter-ions such as sodium; metal complexes (e.g., Zn-protein complexes); and/or non-ionic surfactants such as Tween, PLURONIC™ or polyethylene glycol (PEG).

The polypeptides of the present invention may be optionally administered as a pharmaceutically acceptable salt, such as non-toxic acid addition salts or metal complexes that are commonly used in the pharmaceutical industry. Examples of acid addition salts include organic acids such as acetic, lactic, pamoic, maleic, citric, malic, ascorbic, succinic, benzoic, palmitic, suberic, salicylic, tartaric, methanesulfonic, toluenesulfonic, or trifluoroacetic acids or the like; polymeric acids such as tannic acid, carboxymethyl cellulose, or the like; and inorganic acid such as hydrochloric acid, hydrobromic acid, sulfuric acid phosphoric acid, or the like. Metal complexes include zinc, iron, and the like. In one example, the polypeptide is formulated in the presence of sodium acetate to increase thermal stability.

The active ingredients may also be entrapped in a microcapsule prepared, for example, by coacervation techniques or by interfacial polymerization, for example, hydroxymethylcellulose or gelatin-microcapsule and poly-(methylmethacylate) microcapsule, respectively, in colloidal drug delivery systems (for example, liposomes, albumin microspheres, microemulsions, nano-particles and nanocapsules) or in macroemulsions. Such techniques are disclosed in Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980).

The pharmaceutical composition to be used for in vivo administration typically must be sterile. This may be accomplished by filtration through sterile filtration membranes. Where the composition is lyophilized, sterilization using this method may be conducted either prior to or following lyophilization and reconstitution. The composition for parenteral administration may be stored in lyophilized form or in solution. In addition, parenteral compositions generally are placed into a container having a sterile access port, for example, an intravenous solution bag or vial having a stopper pierceable by a hypodermic injection needle.

Once the pharmaceutical composition has been formulated, it may be stored in sterile vials as a solution, suspension, gel, emulsion, solid, or a dehydrated or lyophilized powder. Such formulations may be stored either in a ready-to-use form or in a form (e.g., lyophilized) requiring reconstitution prior to administration.

VIII. BIOPHYSICAL AND BIOCHEMICAL CHARACTERIZATION

Binding of an anti-PD-L1 Adnectin described herein to PD-L1, e.g., human PD-L1, may be, assessed in terms of equilibrium constants (e.g., dissociation, K_(D)) and in terms of kinetic constants (e.g., on-rate constant, k_(on) and oft-rate constant, k_(off)). An Adnectin will generally bind to a target molecule with a K_(D) of less than 500 nM, 100 nM, 10 nM, 1 nM, 500 pM, 200 pM, or 100 pM, although higher K_(D) values may be tolerated where the k_(off) of is sufficiently low or the k_(on), is sufficiently high.

In Vitro Assays for Binding Affinity

An Anti-PD-L1 Adnectin that binds to and antagonizes PD-L1 can be identified using various in vitro assays. In certain embodiments, the assays are high-throughput assays that allow for screening multiple candidate Adnectins simultaneously.

Exemplary assays for determining the binding affinity of an anti-PD-L1 Adnectin includes, but is not limited to, solution phase methods such as the kinetic exclusion assay (KinExA) (Blake et al, JBC 1996; 271:27677-85; Drake et al., Anal Biochem 2004; 328:35-43), surface plasmon resonance (SPR) with the Biacore system (Uppsala, Sweden) (Welford et al., Opt. Quant. Elect 1991; 23:1; Morton and Myszka, Methods in Enzymology 1998; 295:268) and homogeneous time resolved fluorescence (HTRF) assays (Newton et al., J Biomol Screen 2008; 13:674-82; Patel et al., Assay Drug Dev Technol 2008; 6:55-68).

In certain embodiments, biomolecular interactions can be monitored in real time with the Biacore system, which uses SPR to detect changes in the resonance angle of light at the surface of a thin gold film on a glass support due to changes in the refractive index of the surface up to 300 nm away. Biacore analysis generates association rate constants, dissociation rate constants, equilibrium dissociation constants, and affinity constants. Binding affinity is obtained by assessing the association and dissociation rate constants using a Biacore surface plasmon resonance system (Biacore, Inc.). A biosensor chip is activated for covalent coupling of the target. The target is then diluted and injected over the chip to obtain a signal in response units of immobilized material. Since the signal in resonance units (RU) is proportional to the mass of immobilized material, this represents a range of immobilized target densities on the matrix. Association and dissociation data are fit simultaneously in a global analysis to solve the net rate expression for a 1:1 bimolecular interaction, yielding best fit values for k_(on), k_(off) and R_(max) (maximal response at saturation). Equilibrium dissociation constants for binding, K_(D)'s are calculated from SPR measurements as k_(off)/k_(on).

In some embodiments, the anti-PD-L1 Adnectins described herein exhibit a K_(D) of binding to human PD-L1 in the SPR affinity assay described in Example 2 of 500 nM or less, 400 nM or less, 300 nM or less, 200 nM or less, 150 nM or less, 100 nM or less, 90 nM or less, 80 nM or less, 70 nM or less, 60 nM or less, 50 nM or less, 40 nM or less, 30 nM or less, 20 nM or less, 15 nM or less, 10 nM or less, 5 nM or less, or 1 nM or less.

It should be understood that the assays described herein above are exemplary, and that any method known in the art for determining the binding affinity between proteins (e.g., fluorescence based-transfer (FRET), enzyme-linked immunosorbent assay, and competitive binding assays (e.g., radioimmunoassays)) can be used to assess the binding affinities of the anti-PD-L1 Adnectins described herein.

IX. IN VIVO IMAGING WITH ANTI-PD-L1 ADNECTINS

Imaging Agents

The anti-PD-L1 Adnectins described herein also are useful in a variety of diagnostic and imaging applications. In certain embodiments, an anti-PD-L1 Adnectin is labelled with a moiety that is detectable in vivo and such labelled Adnectins may be used as in vivo imaging agents, e.g., for whole body imaging. For example, in one embodiment, a method for detecting a PD-L1 positive tumor in a subject comprises administering to the subject an anti-PD-L1 Adnectin linked to a detectable label, and following an appropriate time, detecting the label in the subject.

An anti-PD-L1 Adnectin imaging agent may be used to diagnose a disorder or disease associated with increased levels of PD-L1, for example, a cancer in which a tumor selectively overexpresses PD-L1. In a similar manner, an anti-PD-L1 Adnectin can be used to monitor PD-L1 levels in a subject, e.g., a subject that is being treated to reduce PD-L1 levels and/or PD-L1 positive cells (e.g., tumor cells or tumor infiltrating lymphocytes (TILs)) or a subject treated with an immunotherapy, e.g., a PD-1 antagonist. The anti-PD-L1 Adnectin imaging agent may be used to determine whether a subject is likely to respond to a theray that requires the presence of PD-L1, e.g., an immunotherapy, such as a PD-1 or PD-L1 antagonist treatment. The anti-PD-L1 Adnectins may be used with or without modification, and may be labeled by covalent or non-covalent attachment of a detectable moiety.

Detectable moieties that may be used include radioactive agents, such as: radioactive heavy metals such as iron chelates, radioactive chelates of gadolinium or manganese, positron emitters of oxygen, nitrogen, iron, carbon, or gallium, ¹⁸F, ⁶⁰Cu, ⁶¹Cu, ⁶²Cu, ⁶⁴Cu, ¹²⁴I, ⁸⁶Y, ⁸⁹Z ⁶⁶Ga, ⁶⁷Ga, ⁶⁸Ga, ⁴⁴Sc, ⁴⁷Sc, ¹¹C, ¹¹¹In, ^(114m)In, ¹¹⁴In, ¹²⁵I, ¹²⁴I, ¹³¹I, ¹²³I, ¹³¹I, ¹²³I, ³²Cl, ³³Cl, ³⁴Cl, ⁷⁴Br, ⁷⁵Br, ⁷⁶Br, ⁷⁷Br, ⁷⁸Br, ⁸⁹Zr, ¹⁸⁶Re, ¹⁸⁸Re, ⁸⁶Y, ⁹⁰Y, ¹⁷⁷Lu, ⁹⁹Tc, ²¹²Bi, ²¹³Bi, ²¹²Pb, ²²⁵Ac, or ¹⁵³Sm.

In certain embodiments, the radioactive agent is conjugated to the Adnectin at one or more amino acid residues. In certain embodiments, one or more, such as two or more, three or more, four or more, or a greater number of radionuclides can be present in the labelled probe. In certain embodiments, the radionuclide is attached directly to the Adnectin by a chelating agent (e.g., see U.S. Pat. No. 8,808,665). In certain embodiments, the radionuclide is present in a prosthetic group conjugated to the Adnectin by a bifunctional chelator or conjugating (BFC) moiety. In certain embodiments, the radionuclide chelating agent and/or conjugating moiety is DFO, DOTA and its derivatives (CB-DO2A, 3p-C-DEPA, TCMC, Oxo-DO3A), DBCO, TE2A, CB-TE2A, CB-TE1A1P, CB-TE2P, MM-TE2A, DM-TE2A, diamsar and derivatives, NODASA, NODAGA, NOTA, NETA, TACN-TM, DTPA, 1B4M-DTPA, CHX-A″-DTPA, TRAP (PRP9), NOPO, AAZTA and derivatives (DATA), H₂dedpa, H₄octapa, H₂azapa, H₅decapa, H₆phospa, HBED, SHBED, BPCA, CP256, PCTA, HEHA, PEPA, EDTA, TETA, and TRITA based chelating agents, and close analogs and derivatives thereof.

In certain embodiments, the radionuclide chelating or conjugating (BFC) moiety is maleamide-NODAGA or maleamide-DBCO, which can be attached covalently to a polypeptide via cysteine residues near the C-terminus of the polypeptide. In certain embodiments, an anti-PD-L1 Adnectin is modified at its C-terminus by the addition of a cysteine. For example, PxCy may be linked C-terminal to the amino acid residues NYRT, wherein P is proline, C is cysteine, and x and y are integrers that are at least 1. Exemplary anti-PD-L1 Adnectins having the amino acid residues PC at their C-terminus are set forth in the Examples. Maleimide-NODAGA or maleimide-DBCO can be reacted with the cysteine, to yield Adnectin-NODAGA or Adnectin-DBCO, respectively.

In certain embodiments, the radionuclide chelating agent is DFO, which can be attached, e.g., at random surface lysines.

In certain embodiments, the chelator for ⁶⁴Cu is DOTA, NOTA, EDTA, Df, DTPA, or TETA. Suitable combinations of chelating agents and radionuclides are extensively reviewed in Price et al., Chem Soc Rev 2014; 43:260-90.

In certain embodiments, an anti-PD-L1 Adnectin is labelled with the PET tracer ¹⁸F. ¹⁸F is an attractive PET radionuclide with a 1.8 hour radioactive half life, which provides a same day imaging tool, where the PET radionuclide better matches the Adnectin's biological half-life, resulting in excellent images with less radiation exposure to the patient. A PD-L1 Adnectin may be labelled with a prosthetic group, such as [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine ([¹⁸F]-FFPEGA), as further described in the Examples and in FIGS. 2 and 9. As further shown in the Examples, an ¹⁸F-labelled anti-PD-L1 Adnectin specifically and efficiently labelled human PD-L1 positive tumors in mice, PD-L1 positive human lung cancer tissue, and PD-L1 positive tumors in cynomolgus monkeys. Specific details on the labelling method is provided below and in the Examples.

In certain embodiments, a PD-L1 imaging agent is an anti-PD-L1 Adnectin that is labelled with ⁶⁴Cu, e.g., as described in the Examples. ⁶⁴Cu may be linked to an Adnectin with a chelating agent, such as NODAGA. As further shown in the Examples, a ⁶⁴Cu-labelled anti-PD-L1 Adnectin specifically and efficiently labelled human PD-L1 positive tumors in mice and PD-L1 positive tumors in cyno.

Other art-recognized methods for labelling polypeptides with radionuclides such as ⁶⁴Cu and ¹⁸F for synthesizing the anti-PD-L1 Adnectin-based imaging agents described herein and in PCT applications PCT/US15/62485 and PCT/US15/62502 may also be used. See, e.g., US2014/0271467; Gill et al., Nature Protocols 2011; 6:1718-25; Berndt et al. Nuclear Medicine and Biology 2007; 34:5-15, Inkster et al., Bioorganic & Medicinal Chemistry Letters 2013; 23:3920-6, the contents of which are herein incorporated by reference in their entirety.

In certain embodiments, a PD-L1 imaging agent comprises a PEG molecule (e.g., 5 KDa PEG, 6 KDa PEG, 7 KDa PEG, 8 KDa PEG, 9 KDa PEG, or 10 KDa PEG) to increase the blood PK of the imaging agent by small increments to enhance the imaging contrast or increase avidity of the anti-PD-L1 Adnectin based imaging agent.

Administration and Imaging

In certain embodiments, the labeled anti-PD-L1 Adnectins can be used to image PD-L1-positive cells or tissues, e.g., PD-L1 expressing tumors. For example, the labeled anti-PD-L1 Adnectin is administered to a subject in an amount sufficient to uptake the labeled Adnectin into the tissue of interest the PD-L1-expressing tumor). The subject is then imaged using an imaging system such as PET for an amount of time appropriate for the particular radionuclide being used. The labeled anti-PD-L1 Adnectin-bound PD-L1-expressing cells or tissues, e.g., PD-L1-expressing tumors, are then detected by the imaging system.

PET imaging with a PD-L1 imaging agent may be used to qualitatively or quantitatively detect PD-L1. A PD-L1 imaging agent may be used as a biomarker, and the presence or absence of a PD-L1 positive signal in a subject may be indicative that, e.g., the subject would be responsive to a given therapy, e.g., a cancer therapy, or that the subject is responding or not to a therapy.

In certain embodiments, the progression or regression of disease (e.g., tumor) can be imaged as a function of time or treatment. For instance, the size of the tumor can be monitored in a subject undergoing cancer therapy (e.g., chemotherapy, radiotherapy) and the extent of regression of the tumor can be monitored in real-time based on detection of the labeled anti-PD-L1 Adnectin. The distribution of PD-L1 within one or more tumors or healthy cells may, also be visualized, and monitored prior and/or during a treatment and/or a disease.

The amount effective to result in uptake of the imaging agent (e.g., ¹⁸F-Adnectin imaging agent, ⁶⁴Cu-Adnectin imaging agent) into the cells or tissue of interest (e.g., tumors) may depend upon a variety of factors, including for example, the age, body weight, general health, sex, and diet of the host; the time of administration; the route of administration; the rate of excretion of the specific probe employed; the duration of the treatment; the existence of other drugs used in combination or coincidental with the specific composition employed; and other factors.

In certain embodiments, imaging of tissues expressing PD-L1 is effected before, during, and after administration of the labeled anti-PD-L1 Adnectin to a subject.

In certain embodiments, the subject receiving a PD-L1 imaging agent is a mammal, for example, a human, dog, cat, ape, monkey, rat, or mouse.

In certain embodiments, the anti-PD-L1 Adnectins described herein are useful for PET imaging of lungs, heart, kidneys, liver, and skin, and other organs, or tumors associated with these organs which express PD-L1.

In certain embodiments, the anti-PD-L1 imaging agents provide a contrast of at least 50%, 75%, 2, 3, 4, 5 or more. The Examples show that all anti-PD-L1 Adnectins that were used provided a PET contrast of 2 or more, and that the affinity of the Adnectins was not important.

When used for imaging (e.g., PET) with short half-life radionuclides (e.g., ¹⁸F), the radiolabeled anti-PD-L1 Adnectins are preferably administered intravenously, e.g., as a bolus injection. Other routes of administration are also suitable and depend on the half-life of the radionuclides used.

In certain embodiments, the anti-PD-L1 imaging agents described herein are used to detect PD-L1 positive cells in a subject by administering to the subject an anti-PD-L1 imaging agent disclosed herein, and detecting the imaging agent, the detected imaging agent defining the location of the PD-L1 positive cells in the subject. In certain embodiments, the imaging agent is detected by positron emission tomography.

In certain embodiments, the anti-PD-L1 imaging agents described herein are used to detect PD-L1 expressing tumors in a subject by administering to the subject an anti-PD-L1 imaging agent disclosed herein, and detecting the imaging agent, the detected imaging agent defining the location of the tumor in the subject. In certain embodiments, the imaging agent is detected by positron emission tomography.

In certain embodiments, an image of an anti-PD-L1 imaging agent described herein is obtained by administering the imaging agent to a subject and imaging in vivo the distribution of the imaging agent by positron emission tomography.

Disclosed herein are methods of obtaining a quantitative image of tissues or cells expressing PD-L1, the method comprising contacting the cells or tissue with an anti-PD-L1 imaging agent described herein and detecting or quantifying the tissue expressing PD-L1 using positron emission tomography.

Also disclosed herein are methods of detecting a PD-L1-expressing tumor comprising administering an imaging-effective amount of an anti-PD-L1 imaging agent described herein to a subject, e.g., a subject having or suspected of having a PD-L1-expressing tumor, and detecting the radioactive emissions of said imaging agent in the tumor using positron emission tomography, wherein the radioactive emissions are detected in the tumor.

Also disclosed herein are methods of diagnosing the presence of a PD-L1-expressing tumor in a subject, the method comprising

-   -   (a) administering to a subject in need thereof an anti-PD-L1         imaging agent described herein; and     -   (b) obtaining an radio-image of at least a portion of the         subject to detect the presence or absence of the imaging agent;         wherein the presence and location of the imaging agent above         background is indicative of the presence and location of PD-L1         or PD-L1 expressing tumors.

Also provided herein are methods for determining whether a subject having cancer is likely to respond to an immunotherapy, e.g., with a PD-1 or PD-L1 antagonist, the method comprising (a) administering to the subject having cancer a PD-L1 imaging agent, e.g., described herein; and (b) obtaining an image (static or dynamic) of at least a portion of the subject after step (a), and if the subject has a level of PD-L1 in one tumor or across several tumors that is equal to or above that required for treatment with a PD-1 or PD-L1 antagonist (e.g., OPDIVO™, KEYTRUDA™ or TECENTRIQ™), then treating the subject with an anti-tumor therapy, e.g., a PD-1 or PD-L1 antagonist e.g., OPDIVO™, KEYTRUDA™ or TECENTRIQ™.

Also provided herein is a method of treating a subject having cancer, comprising (a) administering to a subject in need thereof an imaging agent comprising a PD-L1 imaging agent, e.g., described herein, and obtaining an image (static or dynamic) of at least a portion of the subject to determine the presence of PD-L1 in one or more tumors; and if the subject has a level of PD-L1 in one tumor or across several tumors that is equal to or above that required for treatment with a PD-1 or PD-L1 antagonist (e.g., OPDIVO™, KEYTRUDA™ or TECENTRIQ™), then, (a) administering to the subject an anti-tumor therapy, e.g., an agent that inhibits the interaction between PD-1 and PD-L1 (a PD-1 or PD-L1 antagonist), e.g., OPDIVO™, KEYTRUDA™ or TECENTRIQ™, to the subject. Also disclosed herein are methods of monitoring the progress of an anti-tumor therapy against PD-L1-expressing tumors in a subject, the method comprising

-   -   (a) administering to a subject in need thereof an anti-PD-L1         imaging agent described herein at a first time point and         obtaining an image of at least a portion of the subject to         determine the size of the tumor;     -   (b) administering an anti-tumor therapy to the subject;     -   (c) administering to the subject the imaging agent at one or         more subsequent time points and obtaining an image of at least a         portion of the subject at each time point;         wherein the dimension and location of the tumor at each time         point is indicative of the progress of the disease.         PET Imaging

Typically, for PET imaging purposes it is desirable to provide the recipient with a dosage of Adnectin that is in the range of from about 0.1 mg to 200 mg as a single intravenous infusion, although a lower or higher dosage also may be administered as circumstances dictate. It may be desirable to provide the recipient with a dosage that is in the range of from about 0.1 mg to 10 mg per square meter of body surface area of the protein or peptide for the typical adult, although a lower or higher dosage also may be administered as circumstances dictate. Examples of dosages of proteins or peptides that may be administered to a human subject for imaging purposes are 10 μg to 1000 μg, 100 μg to 1000 μg, 100 μg to 500 μg, 200 μg to 500 μg, and 300 μg to 400 μg, although higher or lower doses may be used. For example, an ¹⁸F labeled anti-PD-L1 Adnectin, e.g., [¹⁸F]-A02-4PEG-DBCO-FPPEGA or [¹⁸F]E01-4PEG-DBCO-FPPEGA imaging agents may be administered in an amount, e.g., as a bolus injection, to a human ranging from 10 μg to 1000 μg, 100 μg to 1000 μg, 100 μg to 500 μg, 200 μg to 500 μg, and 300 μg to 400 μg. In certain embodiments, an ¹⁸F labeled anti-PD-L1 Adnectin, e.g., [¹⁸F]-A02-4PEG-DBCO-FPPEGA or [¹⁸F]-E01-4PEG-DBCO-FPPEGA imaging agent is administered to a human subject in a n amount of about 350 μg, which corresponds to about 4.4 μg/kg for an 80 kg subject.

In certain embodiments, administration occurs in an amount of radiolabeled Adnectin, e.g., anti-PD-L1 Adnectin, of between 0.005 μg/kg of body weight to 50 μg/kg of body weight per day, e.g., between 0.02 μg/kg of body weight to 10 μg/kg, e.g., per day, between 0.1 μg/kg of body weight to 10 μg/kg of body weight, e.g., per day, between 1 μg/kg of body weight to 10 μg/kg of body weight, e.g., per day, between 2 μg/kg of body weight to 6 μg/kg of body weight, e.g., per day or between 4 μg/kg of body weight to 5 μg/kg of body weight, e.g., per day. The mass associated with a PET tracer is in the form of the natural isotope (e.g., ¹⁹F for a ¹⁸F PET tracer). In certain embodiments, an ¹⁸F labeled anti-PD-L1 Adnectin, e.g., [¹⁸F]-A02-4PEG-DBCO-FPPEGA or [¹⁸F]E01-4PEG-DBCO-FPPEGA imaging agent is administered to a human subject in an amount between 0.1 μg/kg of body weight to 10 μg/kg of body weight, e.g., per day, between 1 μg/kg of body weight to 10 μg/kg of body weight, e.g., per day, between 2 μg/kg of body weight to 6 μg/kg of body weight, e.g., per day or between 4 μg/kg of body weight to 5 μg/kg of body weight, e.g., per day.

Dosage regimens are adjusted to provide the optimum detectable amount for obtaining a clear image of the tissue or cells which uptake the radiolabeled Adnectin. It is especially advantageous to formulate parenteral compositions in dosage unit form for ease of administration and uniformity of dosage. Dosage unit form as used herein refers to physically discrete units suited as unitary dosages for the subjects to which the radiolabeled Adnectin is to be administered. The specification for the dosage unit forms described herein are dictated by and directly dependent on (a) the unique characteristics of the targeting portion of the radiolabeled Adnectin; (b) the tissue or cells to be targeted; (c) the limitations inherent in the imaging technology used.

For administration of the radiolabeled Adnectin, the dosage used will depend upon the disease type, targeting compound used, the age, physical condition, and gender of the subject, the degree of the disease, the site to be examined, and others. In particular, sufficient care has to be taken about exposure doses to a subject. A saturating dose of radiolabel (e.g., ¹⁸F or ⁶⁴Cu) may be administered to the patient. For example, the amount of radioactivity of ¹⁸F-labeled Adnectin may range from 3.7 megabecquerels (MBq) to 3.7 gigabecquerels (GBq), from 18 MBq to 740 MBq, from 100 MBq to 500 MBq, from 100 MBq to 400 MBq, from 100 MBq to 333 MBq, from 100 MBq to 250 MBq, from 150 MBq to 250 MBq, from 200 MBq to 250 MBq or from 200 MBq to 225 MBq. Alternatively, the dosage may be measured in millicuries, for example. In some embodiments, the amount of ¹⁸F imaging agent administered for imaging studies is 1 to 10 mCi, 3 to 10 mCi, 3 to 8 mCi, 4 to 7 mCi or 5 to 6 mCi. In some embodiments, an effective amount will be the amount of compound sufficient to produce emissions in the range of from 1 to 10 mCi, 3 to 10 mCi, 3 to 8 mCi, 4 to 7 mCi or 5 to 6 mCi. In certain embodiments, an ¹⁸F labeled anti-PD-L1 Adnectin, e.g., [¹⁸F]-A02-4PEG-DBCO-FPPEGA or [¹⁸F]E01-4PEG-DBCO-FPPEGA imaging agent is administered to a human subject in an amount of 1 to 10 mCi, 3 to 10 mCi, 3 to 8 mCi, 4 to 7 mCi or 5 to 6 mCi.

In certain embodiments, an ¹⁸F labeled anti-PD-L1 Adnectin, e.g., [¹⁸F]-A02-4PEG-DBCO-FPPEGA or [¹⁸F]E01-4PEG-DBCO-FPPEGA imaging agent, is administered as a composition comprising 1-5% of the ¹⁸F labeled anti-PD-L1 Adnectin, e.g., [¹⁸F]-A02-4PEG-DBCO-FPPEGA or [¹⁸F]E01-4PEG-DBCO-FPPEGA, and 95-99%, respectively, of the non-radiolabeled Adnectin precursor, e.g., PD-L1 Adnectin-4PEG-DBCO. In certain embodiments, the ratio is 2% of the ¹⁸F labeled anti-PD-L1 Adnectin, e.g., [¹⁸F]-A02-4PEG-DBCO-FPPEGA or [¹⁸F]E01-4PEG-DBCO-FPPEGA, and 98%, of the non-radiolabeled Adnectin precursor, e.g., PD-L1 Adnectin-4PEG-DBCO. The ratio may vary, provided that, preferably, the total amount of protein administered to the subject for imaging remains a microdose, i.e., ≤30 nM.

Actual dosage levels of the active ingredients in the pharmaceutical compositions described herein may be varied so as to obtain an amount of the active ingredient which is effective to achieve the desired uptake of the radiolabeled Adnectin in the cells or tissues of a particular patient, composition, and mode of administration, without being toxic to the patient. It will be understood, however, that the total daily usage of the radiolabeled Adnectin of the present disclosure will be decided by the attending physician or other attending professional within the scope of sound medical judgment. The specific effective dose level for any particular subject will depend upon a variety of factors, including for example, the activity of the specific composition employed; the specific composition employed; the age, body weight, general health, sex, and diet of the host; the time of administration; the route of administration; the rate of excretion of the specific compound employed; the duration of the treatment; other drugs, compounds and/or materials used in combination with the particular compositions employed, the age, sex, weight, condition, general health and prior medical history of the patient being treated, and like factors well known in the medical arts. In certain embodiments, the amount of radiolabeled Adnectin administered into a human subject required for imaging will be determined by the prescribing physician with the dosage generally varying according to the quantity of emission from the radionuclide.

In certain embodiments, the radiolabeled Adnectin described herein can be formulated to ensure proper distribution in vivo. For example, the blood-brain barrier (BBB) excludes many highly hydrophilic compounds. Agents may cross the BBB by formulating them, for example, in liposomes. For methods of manufacturing liposomes, see, e.g., U.S. Pat. Nos. 4,522,811; 5,374,548; and 5,399,331. The liposomes may comprise one or more moieties which are selectively transported into specific cells or organs, thus enhance targeted drug delivery (see, e.g., V. V. Ranade (1989) J. Clin. Pharmacol. 29:685). Exemplary targeting moieties include folate or biotin (see, e.g., U.S. Pat. No. 5,416,016 to Low et al.); mannosides (Umezawa et al., (1988) Biochem. Biophys. Res. Commun. 153:1038); antibodies (P. G. Bloeman et al. (1995) FEBS Lett. 357:140; M. Owais et al. (1995) Antimicrob. Agents Chemother. 39:180); surfactant protein A receptor (Briscoe et al. (1995) Am. J. Physiol. 1233:134); p 120 (Schreier et al. (1994) J. Biol. Chem. 269:9090); see also K. Keinanen; M. L. Laukkanen (1994) FEBS Lett. 346:123; J. J. Killion; I. J. Fidler (1994).

Exemplary PET Procedure

The following illustrative procedure may be utilized when performing PET imaging studies on patients in the clinic. A venous catheter, e.g., a 20 G two-inch venous catheter, is inserted into the contralateral ulnar vein for radiotracer administration. Administration of the PET tracer is often timed to coincide with time of maximum (T max) or minimum (T min) of the anti-PD-L1 Adnectin concentration in the blood.

The patient is positioned in the PET camera and a tracer dose of the PET tracer of radiolabeled anti-PD-L1 Adnectin such as [18F]-A02-4PEG-DBCO-FPPEGA or [18F]-E01-4PEG-DBCO-FPPEGA (<20 mCi) is administered via i.v. catheter. A subject may, prior to administration of the PET tracer, drink a liter of water to promote the renal clearance of unbound tracer from the circulation in order to enhance signal to background ratio and/or empty his bladder. Either arterial or venous blood samples may be taken at 15 appropriate time intervals throughout the PET scan in order to, e.g., analyze and quantitate the fraction of unmetabolized PET tracer in plasma. Images may be acquired for up to 120 min. Within ten minutes of the injection of radiotracer and at the end of the imaging session, 1 ml blood samples may be obtained, e.g., for determining the plasma concentration of any labeled or unlabeled anti-PD-L1 Adnectin.

Two types of PET procedures may be used. One type involves obtaining single time point estimates of tracer uptake or static imaging that provides a spatial map of regional tracer concentration. With static imaging, only an average value is measured (e.g. Standardized Uptake Value, SUV). The second type is referred to as dynamic tracer imaging, which can provide considerably more information about in vivo biology by delineating both the temporal and spatial pattern of tracer uptake. See, e.g., Muzi et al. Magn Reson Imaging. 2012 30(9): 1203-1215. PD-L1 Adnectin imaging agents, such as such as [¹⁸F]-A02-4PEG-DBCO-FPPEGA and [¹⁸F]E01-4PEG-DBCO-FPPEGA, may be used in either static tracer imaging or dynamic tracer imaging.

For quantification of tracer uptake, the clinician may visually identify tumor lesions on a PET or CT scan and determine a region-of-interest (ROI) around these lesions. [¹⁸F]PD-L1-uptake in these ROI's may be corrected for body weight and injected dose and quantified as standardized uptake value (SUVmax and SUVmean).

Tomographic images are obtained through image reconstruction. For determining the distribution of radiotracer, ROIs may be drawn on the reconstructed image including, but not limited to, the lungs, liver, heart, kidney, skin, or other organs and tissue (e.g., cancer tissue). Radiotracer uptakes over time in these regions are used to generate time activity curves (TAC) obtained in the absence of any intervention or in the presence of the unlabeled anti-PD-L1 Adnectin at the various dosing paradigms examined. Data may be expressed as radioactivity per unit time per unit volume (μci/cc/mCi injected dose).

PET may be accompanied by a low-dose or diagnostic CT-scan for anatomic reference purposes.

IX EXEMPLARY PET PROCEDURES WITH ¹⁸F LABELED ANTI-PD-L1 ADNECTINS

By labeling a PD-L1 binding agent with Fluoride-18 (¹⁸F), serial [¹⁸F]PD-L1-PET scanning can be used to assess whole body distribution, pharmacokinetics (PK) and pharmacodynamics (PD) and to relate findings to treatment effects. This could help in patient selection and possibly serve as an (early) biomarker for response to PD1/PD-L1 checkpoint inhibitors in the future.

Exemplary PET procedures with ¹⁸F labeled imaging agents, such as ¹⁸F labeled anti-PD-L1 Adnectin imaging agents, e.g., [¹⁸F]-A02-4PEG-DBCO-FPPEGA or [¹⁸F]-E01-4PEG-DBCO-FPPEGA, are as follows.

In one embodiment, a method comprises (a) administering to a subject, e.g., a human, a PD-L1 imaging agent, e.g., an ¹⁸F labeled PD-L1 Adnectin imaging agent, at a dose of about 3-10 mCi (100-333 MBq); and (b) conducting a PET scan of the subject about 1-120 minutes (such as 30-120, 30-60 or 60-120 minutes) after step (a). The PET scan maybe a static PET scan or a dynamic PET scan. If the PET scan is a static PET scan, the PET scan may occur 30-120, 30-60 or 60-120 minutes after administration of the PD-L1 imaging agent, and if the PET scan is a dynamic PET scan, it may occur 1-120, 30-120, 30-60 or 60-120 minutes after administration of the PD-L1 imaging agent, such as 1, 35, 70 and 105 minutes post injection. A dynamic PET scan may take a total duration of 30 to 120 minutes, such as 30 to 60 minutes, e.g., 30 minutes or 60 minutes, with variable frame lengths. The scan may be a whole body scan or a partial body scan, e.g., a scan of a single tumor. For example, a dynamic PET scan may be a scan of a single tumor and a static PET scan may be a whole body scan. In certain embodiments, the dose administered is about 200-225 MBq (i.e., ±10%) or about 6 mCi (i.e., ±10%).

In certain embodiments, a subject is a subject with cancer, and the method comprises (a) administering to the subject a PD-L1 imaging agent, e.g., an ¹⁸F labeled PD-L1 Adnectin imaging agent, at a dose of about 3-10 mCi (100-333 MBq); and (b) conducting a PET scan of the subject about 1-120 minutes (such as 30-120, 30-60 or 60-120 minutes) after step (a), wherein steps (a) and (b) are conducted prior to the initiation of a cancer treatment. In certain embodiments, a subject is a subject with cancer, and the method comprises (a) administering to the subject a PD-L1 imaging agent, e.g., an ¹⁸F labeled PD-L1 Adnectin imaging agent, at a dose of about 3-10 mCi (100-333 MBq); and (b) conducting a PET scan of the subject about 1-120 minutes (such as 30-120, 30-60 or 60-120 minutes) after step (a), wherein steps (a) and (b) are conducted at at least 2 time points, e.g., one of which is prior to the initiation of a cancer treatment, and one of which is during the cancer treatment, or wherein both time points are during the cancer treatment. The two time points may be separated by, e.g., a time of 1-10 weeks, such as 2-8 weeks, such as 5-7 weeks, such as 6 weeks. In certain embodiments, steps (a) and (b) are conducted at at least 3, 4, 5 or more time points, wherein the successive time points are separated by, e.g., a time of 1-10 weeks, such as 2-8 weeks, such as 5-7 weeks, such as 6 weeks.

In certain embodiments, a subject is a subject with cancer and the subject is being treated with an immunotherapy, e.g., a PD-1 antagonist and/or a PD-L1 antagonist, and the method comprises (a) administering to the subject a PD-L1 imaging agent, e.g., an ¹⁸F labeled PD-L1 Adnectin imaging agent, at a dose of about 3-10 mCi (100-333 MBq); and (b) conducting a PET scan of the subject about 1-120 minutes (such as 30-120, 30-60 or 60-120 minutes) after step (a), wherein steps (a) and (b) are conducted at at least 2, 3, 4 or 5 time points, e.g., one of which is prior to the initiation of the immunotherapy treatment, and one of which is during the immunotherapy treatment, or wherein both time points are during the immunotherapy treatment.

In certain embodiments, a subject is a subject with cancer and the subject is being treated with an immunotherapy, e.g., a PD-1 antagonist and/or a PD-L1 antagonist, and the method comprises (a) administering to the subject a PD-L1 imaging agent, e.g., an ¹⁸F labeled PD-L1 Adnectin imaging agent, at a dose of about 3-10 mCi (100-333 MBq); and (b) conducting a PET scan of the subject about 1-120 minutes (such as 30-120, 30-60 or 60-120 minutes) after step (a), wherein steps (a) and (b) are conducted at at least 1, 2, 3, 4 or 5 time points, e.g., one of which is prior to the initiation of the immunotherapy treatment, and if there are more than one iteration of steps (a) and (b), one of which is during the immunotherapy treatment, or wherein all time points are during the immunotherapy treatment, and wherein the results of the PET scan are informative for further treatment of the subject. For example, the results of the PET scan may indicate that the tumors of the subject are not reduced in size during the treatment, which suggests that the treatment may not be successful and should be changed or stopped.

Alternatively, a first scan, prior to treatment, may indicate that the subject does not express PD-L1 in a majority of tumors, and that a treatment with a PD-1 antagonist and/or a PD-L1 antagonist, would not be successful. Accordingly, provided herein is a method of treating a subject having cancer, comprising

-   -   (a) administering to a subject in need thereof an imaging agent         comprising an anti-PD-L1 Adnectin, and obtaining an image         (static or dynamic) of at least a portion of the subject to         determine the presence of PD-L1 in one or more tumors; and, if         PD-L1 is detected in one or more tumors, then,     -   (b) administering to the subject an anti-tumor therapy, e.g., an         agent that inhibits the interaction between PD-1 and PD-L1 (a         PD-1 or PD-L1 antagonist), e.g., OPDIVO™, KEYTRUDA™ or         TECENTRIQ™.

Also provided is a method of predicting whether a subject having cancer is likely to respond to a therapy with a PD-1 or PD-L1 antagonist, comprising (a) administering to a subject in need thereof an imaging agent comprising an anti-PD-L1 Adnectin, and obtaining an image (static or dynamic) of at least a portion of the subject to determine the presence of PD-L1 in one or more tumors; and, if PD-L1 is detected in one or more tumors, then, the subject is likely to respond to a therapy with a PD-1 or PD-L1 antagonist.

The methods may comprise administering an anti-tumor therapy when at least 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95% of the cells in a tumor specimen are PD-L1 positive, or on average across several tumors. In certain embodiments, an anti-tumor therapy, e.g., a PD-1 or PD-L1 antagonist, is not administered to the subject, unless the subject is PD-L1 positive in at least 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95% of the cells in a tumor specimen, or on average across several tumors. In certain embodiments, an anti-tumor therapy is administered if the level of PD-L1 detected in one or more tumors is at least equal to the level of PIMA that is necessary for receiving treatment with an a PD-1 or PD-L1 antagonist therapeutic.

Methods in which more than one iteration of steps (a) and (b) are used may comprise comparing a PET scan conducted at a first time point with a PET scan conducted at a second time point, and/or later time point. Such comparison may inform on a patient's evolution of the disease, a patient's response to a treatment, a patient's potential adverse reaction or other.

In certain embodiments, a subject is a subject with cancer and the subject is being treated with an immunotherapy, e.g., a PD-1 antagonist and/or a PD-L1 antagonist, and the method comprises (a) administering to the subject a PD-L1 imaging agent, e.g., an ¹⁸F labeled PD-L1 Adnectin imaging agent, at a dose of about 3-10 mCi (100-333 MBq); and (b) conducting a PET scan of the subject about 1-120 minutes (such as 30-120, 30-60 or 60-120 minutes) after step (a), wherein steps (a) and (b) are conducted at at least 1, 2, 3, 4 or 5 time points, e.g., one of which is prior to the initiation of the immunotherapy treatment, and if there are more than one iteration of steps (a) and (b), one of which is during the immunotherapy treatment, or wherein all time points are during the immunotherapy treatment, wherein the ¹⁸F labeled PD-L1 Adnectin imaging agent comprises one of the following:

-   -   the modified loops BC, DE and FG of the A02 Adnectin (i.e., SEQ         ID NOs: 81, 82 and 83); or wherein one of these loops differs in         one amino acid deletion, addition or substitution relative to         the corresponding loop in the A02 Adnectin; wherein two of these         loops each differ in one amino acid deletion, addition or         substitution (e.g., conservative amino acid substitution)         relative to the corresponding loops in the A02 Adnectin; or         wherein three of these loops each differ in one amino acid         deletion, addition or substitution relative to the corresponding         loops in the A02 Adnectin, and wherein the Adnectin binds         specifically to human PD-L1 as determined by Biacore;     -   the modified loops BC, DE and FG of the E01 Adnectin (i.e., SEQ         ID NOs: 97, 98 and 99); or wherein one of these loops differs in         one amino acid deletion, addition or substitution relative to         the corresponding loop in the E01 Adnectin; wherein two of these         loops each differ in one amino acid deletion, addition or         substitution (e.g., conservative amino acid substitution)         relative to the corresponding loops in the E01 Adnectin; or         wherein three of these loops each differ in one amino acid         deletion, addition or substitution relative to the corresponding         loops in the E01 Adnectin, and wherein the Adnectin binds         specifically to human PD-L1 as determined by Biacore;     -   an amino acid sequence that is at least 95%, 96%, 97%, 98%, 99%         or 100% identical to an amino acid sequence of the A02 Adnectin         (e.g., any one of SEQ ID NOs: 80, and 84-91) or the E01 Adnectin         (e.g., any one of SEQ ID NOs: 96, 100-107), wherein a         substitution may be a conservative substitution, and wherein the         Adnectin binds specifically to human PD-L1 as determined by         Biacore; and/or     -   an amino acid sequence that differs from the amino acid sequence         of the A02 Adnectin, comprising, e.g., any one of SEQ ID NOs:         80, and 84-91 or the E01 Adnectin comprising, e.g., any one of         SEQ ID NOs: 96, 100-107, in 1-10 amino acid deletions, additions         or substitutions (e.g., conservative substitutions), wherein a         substitution may be a conservative substitution, and wherein the         Adnectin binds specifically to human PD-L1 as determined by         Biacore.

In certain embodiments, a subject is a subject with cancer and the subject is being treated with an immunotherapy, e.g., a PD-1 antagonist and/or a PD-L1 antagonist, and the method comprises (a) administering to the subject a PD-L1 imaging agent, e.g., an ¹⁸F labeled PD-L1 Adnectin imaging agent, at a dose of about 3-10 mCi (100-333 MBq); and (b) conducting a PET scan of the subject about 1-120 minutes (such as 30-120, 30-60 or 60-120 minutes) after step (a), wherein steps (a) and (b) are conducted at at least 1, 2, 3, 4 or 5 time points, e.g., one of which is prior to the initiation of the immunotherapy treatment, and if there are more than one iteration of steps (a) and (b), one of which is during the immunotherapy treatment, or wherein all time points are during the immunotherapy treatment, wherein the ¹⁸F labeled PD-L1 Adnectin imaging agent is [¹⁸F]-A02-4PEG-DBCO-FPPEGA, wherein the A02 Adnectin comprises any one of SEQ ID NOs: 80 and 84-91, or [¹⁸F]E01-4PEG-DBCO-FPPEGA, wherein the E01 Adnectin comprises any one of SEQ ID NOs: 96 and 100-107, and the structure of 4PEG-DBCO-FPPEGA is the structure provided in FIG. 2 or 9. The composition that is administered to a subject may be a composition wherein 2% of the molecules are [¹⁸F]-A02-4PEG-DBCO-FPPEGA or [¹⁸F]-E01-4PEG-DBCO-FPPEGA and 98% of the molecules are A02-4PEG-DBCO or E01-4PEG-DBCO, respectively, and where, preferably, equal or less than 30 nM of total protein is administered to the subject in one tracer administration.

Also provided herein are methods for determining whether a subject having cancer is likely to respond to an immunotherapy, e.g., with a PD-1 or PD-L1 antagonist, the method comprising (a) administering to the subject having cancer a PD-L1 imaging agent, e.g., an ¹⁸F labeled PD-L1 Adnectin imaging agent, at a dose of about 3-10 mCi (100-333 MBq); and (b) conducting a PET scan of the subject about 1-120 minutes (such as 30-120, 30-60 or 60-120 minutes) after step (a), and if the subject has a level of PD-L1 in one tumor or across several tumors that is equal to or above that required for treatment with a PD-1 or PD-L1 antagonist (e.g., OPDIVO™, KEYTRUDA™ or TECENTRIQ™), then the subject is likely to respond to an anti-tumor therapy, e.g., a PD-1 or PD-L1 antagonist e.g., OPDIVO™, KEYTRUDA™ or TECENTRIQ™, wherein the ¹⁸F labeled PD-L1 Adnectin imaging agent comprises one of the following:

-   -   the modified loops BC, DE and FG of the A02 Adnectin (i.e., SEQ         ID NOs: 81, 82 and 83); or wherein one of these loops differs in         one amino acid deletion, addition or substitution relative to         the corresponding loop in the A02 Adnectin; wherein two of these         loops each differ in one amino acid deletion, addition or         substitution (e.g., conservative amino acid substitution)         relative to the corresponding loops in the A02 Adnectin; or         wherein three of these loops each differ in one amino acid         deletion, addition or substitution relative to the corresponding         loops in the A02 Adnectin, and wherein the Adnectin binds         specifically to human PD-L1 as determined by Biacore;     -   the modified loops BC, DE and FG of the E01 Adnectin (i.e., SEQ         ID NOs: 97, 98 and 99); or wherein one of these loops differs in         one amino acid deletion, addition or substitution relative to         the corresponding loop in the E01 Adnectin; wherein two of these         loops each differ in one amino acid deletion, addition or         substitution (e.g., conservative amino acid substitution)         relative to the corresponding loops in the E01 Adnectin; or         wherein three of these loops each differ in one amino acid         deletion, addition or substitution relative to the corresponding         loops in the E01 Adnectin, and wherein the Adnectin binds         specifically to human PD-L1 as determined by Biacore;     -   an amino acid sequence that is at least 95%, 96%, 97%, 98%, 99%         or 100% identical to an amino acid sequence of the A02 Adnectin         (e.g., any one of SEQ ID NOs: 80, and 84-91) or the E01 Adnectin         (e.g., any one of SEQ ID NOs: 96, 100-107), wherein a         substitution may be a conservative substitution, and wherein the         Adnectin binds specifically to human PD-L1 as determined by         Biacore; and/or     -   an amino acid sequence that differs from the amino acid sequence         of the A02 Adnectin, comprising, e.g., any one of SEQ ID NOs:         80, and 84-91 or the E01 Adnectin comprising, e.g., any one of         SEQ ID NOs: 96, 100-107, in 1-10 amino acid deletions, additions         or substitutions (e.g., conservative substitutions), wherein a         substitution may be a conservative substitution, and wherein the         Adnectin binds specifically to human PD-L1 as determined by         Biacore.

Provided herein is a method of treating a subject having cancer, comprising (a) administering to the subject a PD-L1 imaging agent, e.g., an ¹⁸F labeled PD-L1 Adnectin imaging agent, at a dose of about 3-10 mCi (100-333 MBq); and (b) conducting a PET scan of the subject about 1-120 minutes (such as 30-120, 30-60 or 60-120 minutes) after step (a), and if the subject has a level of PD-L1 in one tumor or across several tumors that is equal to or above that required for treatment with a PD-1 or PD-L1 antagonist (e.g., OPDIVO™, KEYTRUDA™ or TECENTRIQ™), then administering to the subject an anti-tumor therapy, e.g., a PD-1 or PD-L1 antagonist e.g., OPDIVO™, KEYTRUDA™ or TECENTRIQ™, wherein the ¹⁸F labeled PD-L1 Adnectin imaging agent comprises one of the following:

-   -   the modified loops BC, DE and FG of the A02 Adnectin (i.e., SEQ         ID NOs: 81, 82 and 83); or wherein one of these loops differs in         one amino acid deletion, addition or substitution relative to         the corresponding loop in the A02 Adnectin; wherein two of these         loops each differ in one amino acid deletion, addition or         substitution (e.g., conservative amino acid substitution)         relative to the corresponding loops in the A02 Adnectin; or         wherein three of these loops each differ in one amino acid         deletion, addition or substitution relative to the corresponding         loops in the A02 Adnectin, and wherein the Adnectin binds         specifically to human PD-L1 as determined by Biacore;     -   the modified loops BC, DE and FG of the E01 Adnectin (i.e., SEQ         ID NOs: 97, 98 and 99); or wherein one of these loops differs in         one amino acid deletion, addition or substitution relative to         the corresponding loop in the E01 Adnectin; wherein two of these         loops each differ in one amino acid deletion, addition or         substitution (e.g., conservative amino acid substitution)         relative to the corresponding loops in the E01 Adnectin; or         wherein three of these loops each differ in one amino acid         deletion, addition or substitution relative to the corresponding         loops in the E01 Adnectin, and wherein the Adnectin binds         specifically to human PD-L1 as determined by Biacore;     -   an amino acid sequence that is at least 95%, 96%, 97%, 98%, 99%         or 100% identical to an amino acid sequence of the A02 Adnectin         (e.g., any one of SEQ ID NOs: 80, and 84-91) or the E01 Adnectin         (e.g., any one of SEQ ID NOs: 96, 100-107), wherein a         substitution may be a conservative substitution, and wherein the         Adnectin binds specifically to human PD-L1 as determined by         Biacore; and/or     -   an amino acid sequence that differs from the amino acid sequence         of the A02 Adnectin, comprising, e.g., any one of SEQ ID NOs:         80, and 84-91 or the E01 Adnectin comprising, e.g., any one of         SEQ ID NOs: 96, 100-107, in 1-10 amino acid deletions, additions         or substitutions (e.g., conservative substitutions), wherein a         substitution may be a conservative substitution, and wherein the         Adnectin binds specifically to human PD-L1 as determined by         Biacore.

Provided herein is a method of treating a subject having cancer, comprising (a) administering to the subject a PD-L1 imaging agent, e.g., an ¹⁸F labeled PD-L1 Adnectin imaging agent, at a dose of about 3-10 mCi (100-333 MBq); and (b) conducting a PET scan of the subject about 1-120 minutes (such as 30-120, 30-60 or 60-120 minutes) after step (a), and if the subject has a level of PD-L1 in one tumor or across several tumors that is equal to or above that required for treatment with a PD-1 or PD-L1 antagonist (e.g., OPDIVO™, KEYTRUDA™ or TECENTRIQ™), then administering to the subject an anti-tumor therapy, e.g., a PD-1 or PD-L1 antagonist e.g., OPDIVO™, KEYTRUDA™ or TECENTRIQ™, to the subject, the ¹⁸F labeled PD-L1 Adnectin imaging agent is [¹⁸F]-A02-4PEG-DBCO-FPPEGA, wherein the A02 Adnectin comprises any one of SEQ ID NOs: 80 and 84-91, or [¹⁸F]E01-4PEG-DBCO-FPPEGA, wherein the E01 Adnectin comprises any one of SEQ ID NOs: 96 and 100-107, and the structure of 4PEG-DBCO-FPPEGA is the structure provided in FIG. 2 or 9. The composition that is administered to a subject may be a composition wherein 2% of the molecules are [¹⁸F]-A02-4PEG-DBCO-FPPEGA or [¹⁸F]-E01-4PEG-DBCO-FPPEGA and 98% of the molecules are A02-4PEG-DBCO or E01-4PEG-DBCO, respectively, and where, preferably, equal or less than 30 nM of total protein is administered to the subject in one tracer administration.

X. DETECTION OF PD-L1 WITH ANTI-PD-L1 ADNECTINS

In addition to detecting PD-L1 in vivo, anti-PDL1 Adnectins, such as those described herein, may be used for detecting a target molecule in a sample. A method may comprise contacting the sample with an anti-PD-L1 Adnectins described herein, wherein said contacting is carried out under conditions that allow anti-PD-L1 Adnectin-target complex formation; and detecting said complex, thereby detecting said target in said sample. Detection may be carried out using any art-recognized technique, such as, e.g., radiography, immunological assay, fluorescence detection, mass spectroscopy, or surface plasmon resonance. The sample may be from a human or other mammal. For diagnostic purposes, appropriate agents are detectable labels that include radioisotopes, for whole body imaging, and radioisotopes, enzymes, fluorescent labels and other suitable antibody tags for sample testing.

The detectable labels can be any of the various types used currently in the field of in vitro diagnostics, including particulate labels including metal sols such as colloidal gold, isotopes such as I¹²⁵ or Tc⁹⁹ presented for instance with a peptidic chelating agent of the N₂S₂, N₃S or N₄ type, chromophores including fluorescent markers, biotin, luminescent markers, phosphorescent markers and the like, as well as enzyme labels that convert a given substrate to a detectable marker, and polynucleotide tags that are revealed following amplification such as by polymerase chain reaction. A biotinylated antibody would then be detectable by avidin or streptavidin binding. Suitable enzyme labels include horseradish peroxidase, alkaline phosphatase and the like. For instance, the label can be the enzyme alkaline phosphatase, detected by measuring the presence or formation of chemiluminescence following conversion of 1,2 dioxetane substrates such as adamantyl methoxy phosphoryloxy phenyl dioxetane (AMPPD), disodium 3-(4-(methoxyspiro{1,2-dioxetane-3,2′-(5′-chloro)tricyclo{3.3.1.1 3,7}decan}-4-yl) phenyl phosphate (CSPD), as well as CDP and CDP-Star® or other luminescent substrates well-known to those in the art, for example the chelates of suitable lanthanides such as Terbium (III) and Europium (III). Other labels include those set forth above in the imaging section. The detection means is determined by the chosen label. Appearance of the label or its reaction products can be achieved using the naked eye, in the case where the label is particulate and accumulates at appropriate levels, or using instruments such as a spectrophotometer, a luminometer, a fluorimeter, and the like, all in accordance with standard practice.

In certain embodiments, conjugation methods result in linkages which are substantially (or nearly) non-immunogenic, e.g., peptide- (i.e. amide-), sulfide-, (sterically hindered), disulfide-, hydrazone-, and ether linkages. These linkages are nearly non-immunogenic and show reasonable stability within serum (see e.g. Senter, P. D., Curr. Opin. Chem. Biol. 13 (2009) 235-244; WO 2009/059278; WO 95/17886).

Depending on the biochemical nature of the moiety and Adnectin, different conjugation strategies can be employed. In case the moiety is naturally occurring or recombinant polypeptide of between 50 to 500 amino acids, there are standard procedures in textbooks describing the chemistry for synthesis of protein conjugates, which can be easily followed by the skilled artisan (see e.g. Hackenberger, C. P. R., and Schwarzer, D., Angew. Chem. Int. Ed. Engl. 47 (2008) 10030-10074). In one embodiment the reaction of a maleinimido moiety with a cysteine residue within the Adnectin or the moiety is used. Alternatively, coupling to the C-terminal end of the Adnectin is performed. C-terminal modification of a protein can be performed as described in, e.g., Sunbul, M. and Yin, J., Org. Biomol. Chem. 7 (2009) 3361-3371). When the moiety is a peptide or polypeptide, the Adnectin and moiety can be fused by standard genetic fusion, optionally with a linker disclosed herein.

In general, site specific reaction and covalent coupling is based on transforming a natural amino acid into an amino acid with a reactivity which is orthogonal to the reactivity of the other functional groups present. For example, a specific cysteine within a rare sequence context can be enzymatically converted in an aldehyde (see Frese, M. A., and Dierks, T., Chem Bio Chem. 10 (2009) 425-427). It is also possible to obtain a desired amino acid modification by utilizing the specific enzymatic reactivity of certain enzymes with a natural amino acid in a given sequence context (see, e.g., Taki, M. et al., Prot. Eng. Des. Sel. 17 (2004) 119-126; Gautier, A. et al. Chem. Biol. 15 (2008) 128-136. Protease-catalyzed formation of C—N bonds is described at Bordusa, F., Highlights in Bioorganic Chemistry (2004) 389-403.

Site specific reaction and covalent coupling can also be achieved by the selective reaction of terminal amino acids with appropriate modifying reagents. The reactivity of an N-terminal cysteine with benzonitrils (see Ren, H. et al., Angew. Chem. Int. Ed. Engl. 48 (2009) 9658-9662) can be used to achieve a site-specific covalent coupling. Native chemical ligation can also rely on C-terminal cysteine residues (Taylor, E. Vogel; Imperiali, B, Nucleic Acids and Molecular Biology (2009), 22 (Protein Engineering), 65-96). EP 1 074 563 describes a conjugation method which is based on the faster reaction of a cysteine within a stretch of negatively charged amino acids than a cysteine located in a stretch of positively charged amino acids.

The moiety may also be a synthetic peptide or peptide mimic. In case a polypeptide is chemically synthesized, amino acids with orthogonal chemical reactivity can be incorporated during such synthesis (see e.g. de Graaf, A. J. et al., Bioconjug. Chem. 20 (2009) 1281-1295). Since a great variety of orthogonal functional groups is at stake and can be introduced into a synthetic peptide, conjugation of such peptide to a linker is standard chemistry.

In order to obtain a mono-labeled polypeptide the conjugate with 1:1 stoichiometry may be separated by chromatography from other conjugation side-products. This procedure can be facilitated by using a dye labeled binding pair member and a charged linker. By using this kind of labeled and highly negatively charged binding pair member, mono conjugated polypeptides are easily separated from non-labeled polypeptides and polypeptides which carry more than one linker, since the difference in charge and molecular weight can be used for separation. The fluorescent dye can be useful for purifying the complex from un-bound components, like a labeled monovalent binder.

XI. SYNTHESIS OF ¹⁸F-LABELED ANTI-PD-L1 ADNECTINS

¹⁸F-labeled anti-PD-L1 Adnectins may be synthesized by first preparing an ¹⁸F radiolabeled prosthetic group, linking an Adnectin to a bifunctional chelating agent, and then combining these two reagents (see, e.g., FIG. 9).

¹⁸F Radiolabeled Prosthetic Groups

In one aspect, provided herein is an ¹⁸F-radiolabeled compound containing a prosthetic group for use in a bioorthogonal reaction involving 1,3-dipolar cycloaddition between an azide and a cyclooctyne which proceeds selectively under water tolerant conditions. The ¹⁸F-radiolabeled prosthetic groups disclosed herein are soluble in 100% aqueous, and there is no need for an organic phase to link the prosthetic groups to the anti-PD-L1 Adnectins disclosed herein. This feature is particularly advantageous as there is no need for an organic phase to link the prosthetic group to the anti-PD-L1 Adnectins, which cannot withstand even small amounts of organic solvents, given degradation and aggregation issues.

Additionally, unlike aliphatic prosthetic groups, the ¹⁸F fluorination reaction can be monitored with UV, and the ¹⁸F-radiolabeled prosthetic groups described herein are not volatile. Moreover, the ¹⁸F-radiolabeled prosthetic groups can be incorporated into the anti-PD-L1 Adnectins using a copper free click chemistry, e.g., as described in the Examples, thus avoiding the stability issues observed in some biologics when copper mediated click chemistry is used.

In one aspect, provided herein is a PEGylated ¹⁸F-pyridine covalently bound to an azide with the following structure,

wherein x is an integer from 1 to 8. In certain embodiments, x is an integer from 2 to 6. In some embodiments x is an integer from 3 to 5. In certain embodiments, x is 4. In certain embodiments, ¹⁸F is attached to the pyridine ortho to the N atom. In certain embodiments, the [O(CH₂)₂]_(x) moiety is present in the 1-3 configuration relative to the nitrogen on the pyridine ring. In certain embodiments, the [O(CH₂)₂]_(x) moiety is present in the 1-2 configuration relative to the nitrogen on the pyridine ring. In certain embodiments, the [O(CH₂)₂]_(x) moiety is present in the 1-4 configuration relative to the nitrogen on the pyridine ring.

In certain embodiments, the ¹⁸F-radiolabeled compound has the structure

wherein x is an integer from 1 to 8. In certain embodiments, x is an integer from 2 to 6. In some embodiments x is an integer from 3 to 5. In certain embodiments, x is 4.

In certain embodiments, the ¹⁸F-radiolabeled compound has the structure

wherein x is an integer from 1 to 8. In certain embodiments, x is an integer from 2 to 6. In certain embodiments x is an integer from 3 to 5. In certain embodiments, x is 4.

In certain embodiments, the ¹⁸F-radiolabeled compound is [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine (¹⁸F-FPPEGA) and has the structure

In certain embodiments, the ¹⁸F-radiolabeled prosthetic group may contain additional groups on the pyridine ring which do not interfere with the fluorination reaction. In certain embodiments, additions to the pyridine ring include C₁₋₆ alkyl groups, for example methyl, ethyl and propyl.

In certain embodiments, the ¹⁸F-radiolabeled prosthetic group is a fused ring system with the following structure:

wherein “OPEG” is [O(CH₂)₂]_(x), and x is an integer from 1 to 8. In certain embodiments, x is an integer from 2 to 6. In certain embodiments x is an integer from 3 to 5. In certain embodiments, x is 4.

The ¹⁸F-radiolabeled prosthetic groups described herein may be produced using chemical reactions described in the Examples herein.

Also provided herein is a method of preparing a PEGylated ¹⁸F-pyridine covalently bound to an azide with the following structure,

wherein x is an integer from 1 to 8, the method comprising the steps of

(a) providing a solution of a compound a with the following structure:

wherein x is an integer from 1 to 8, and R is NO2, Br, F or

and is ortho to the N atom of the pyridine ring;

(b) providing a mixture of ¹⁸F in ¹⁸O water, 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane and a weak base;

(c) drying the mixture from step b) to form a solid; and

(d) reacting the solution from step a) with the solid from step c) to form the ¹⁸F-labeled compound.

In certain embodiments, the method produces a ¹⁸F-pyridine prosthetic group with the following structure b

(where ¹⁸F is ortho to the N atom), and includes the steps of

(a) providing a solution of the compound of the structure

(where X is ortho to the N atom) where X is NO₂, Br or

(b) providing a mixture of ¹⁸F in ¹⁸O water, 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane and weak base, such as K₂CO₃;

(c) drying the mixture from step b) to form a solid; and

(d) reacting the solution from step a) with the solid from step c) to form the ¹⁸F-labeled compound.

In certain embodiments, the method further comprises the step of producing a compound with the following structure a

according to the Scheme I shown below:

In certain embodiments, the method comprises producing ¹⁸F-pyridine prosthetic group is [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine (¹⁸F-FPPEGA), e, from d according to the following reaction conditions:

¹⁸F-Radiolabeled PD-L1 Adnectins

In some aspects, provided herein are ¹⁸F-radiolabeled probes or agents with the following structure,

wherein the Protein is a PD-L1 Adnectin and x is an integer from 1 to 8. In certain embodiments, x is an integer from 2 to 6. In certain embodiments x is an integer from 3 to 5. In some embodiments, x is 4. BFC

Bifunctional chelating or conjugating (BFC) moieties, which can be used in the ¹⁸F-radiolabled compositions disclosed herein are commercially available (e.g., Sigma Aldrich; Click Chemistry Tools), or may be synthesized according to well-known chemical reactions.

In certain embodiments, the BFC is selected from cyclooctyne based chelating agents (e.g., DBCO, DIBO), DFO, DOTA and its derivatives (CB-DO2A, 3p-C-DEPA, TCMC, Oxo-DO3A), TE2A, CB-TE2A, CB-TE1A1P, CB-TE2P, MM-TE2A, DM-TE2A, diamsar and derivatives, NODASA, NODAGA, NOTA, NETA, TACN-TM, DTPA, 1B4M-DTPA, CHX-A″-DTPA, TRAP (PRP9), NOPO, AAZTA and derivatives (DATA), H2dedpa, H₄octapa, H₂azapa, H₅decapa, H₆phospa, HBED, SHBED, BPCA, CP256, PCTA, HEHA, PEPA, EDTA, TETA, and TRITA based chelating agents, and close analogs and derivatives thereof. Suitable combinations of chelating agents and radionuclides are extensively described in Price et al., Chem Soc Rev 2014; 43:260-90.

In certain embodiments, the BFC is a cyclooctyne comprising a reactive group that forms a covalent bond with an amine, carboxyl, carbonyl or thiol functional group on the targeting protein or peptide. Reactive groups on the cyclooctyne include esters, acids, hydroxyl groups, aminooxy groups, malaiemides, α-halogenketones and α-halogenacetamides.

In certain embodiments, the BFC is a cyclooctyne is dibenzocyclooctyne (DIBO), biarylazacyclooctynone (BARAC), dimethoxyazacyclooctyne (DIMAC) and dibenzocyclooctyne (DBCO). In certain embodiments, the cyclootyne is DBCO.

In certain embodiments, the cyclooctyne comprises a hydrophilic polyethylene glycol (PEG)_(y) spacer arm, wherein y is an integer from 1 to 8. In certain embodiments, y is an integer from 2 to 6. In certain embodiments, y is 4 or 5.

In certain embodiments, the BFC is DBCO-PEG4-NHS-Ester or DBCO-Sulfo-NHS-Ester which react specifically and efficiently with a primary amine (e.g., side chain of lysine residues or aminosilane-coated surfaces). In certain embodiments, the BFC is DBCO-PEG4-Acid with terminal carboxylic acid (—COOH) that can be reacted with primary or secondary amine groups in the presence activators (e.g. EDC) forming a stable amide bond. In certain embodiments, the BFC is DBCO-PEG4-Amine which reacts with carboxyl groups in the presence of activators (e.g. EDC, or DCC) or with activated esters (e.g. NHS esters) forming stable amide bonds.

In certain embodiments, the BFC is DBCO-PEG4-Maleimide which reacts with sulfhydryl groups on cysteine residues, e.g., at or near the C-terminus of the polypeptide.

In certain embodiments, the polypeptide is modified at its C-terminus by the addition of a cysteine. For example, P_(m)C_(n) may be linked to the C-terminal amino acid residue of the polypeptide, wherein P is proline, C is cysteine, m is an integer that at least 0 and n is an integer that is at least 1. Methods for making such modifications are well-known in the art.

In certain embodiments, the ¹⁸F-radiolabeled probe or agent has the following structure a,

wherein the BFC is conjugated to the protein (e.g., an anti-PD-L1 Adnectin) at a cysteine residue.

The ¹⁸F-radiolabeled targeting agents described herein are produced using bioorthogonal, metal free click chemistry in medium suitable for direct use in vivo (e.g., saline) according to the procedures described herein.

XIII. KITS AND ARTICLES OF MANUFACTURE

The anti-PD-L1 Adnectins described herein can be provided in a kit, a packaged combination of reagents in predetermined amounts with instructions for use in the methods described herein.

For example, in certain embodiments, an article of manufacture containing materials useful for the treatment or prevention of the disorders or conditions described herein, or for use in the methods of detection described herein, are provided. The article of manufacture comprises a container and a label. Suitable containers include, for example, bottles, vials, syringes, and test tubes. The containers may be formed from a variety of materials such as glass or plastic. The container may hold a composition described herein for in vivo imaging, and may have a sterile access port (for example the container may be an intravenous solution bag or a vial having a stopper pierceable by a hypodermic injection needle). The active agent in the composition is an anti-PD-L1 Adnectin or derivative or precursor thereof, e.g., as described herein. The article of manufacture may further comprise a second container comprising a pharmaceutically-acceptable buffer, such as phosphate-buffered saline, Ringer's solution and dextrose solution. It may further include other materials desirable from a commercial and user standpoint, including other buffers, diluents, filters, needles, syringes, and package inserts with instructions for use.

In certain embodiments, a kit comprises one or more reagents necessary for forming an ¹⁸F labelled anti-PD-L1 Adnectin in vivo imaging agent, such as a [¹⁸F]-PD-L1 Adnectin-4-PEG-DBCO-FPPEGA, as further described herein. For example, a kit may comprise a first vial comprising a PD-L1 Adnectin-4-PEG-DBCO and a second vial comprising [¹⁸F]FPPEGA. A kit may comprise a first vial comprising a PD-L1 Adnectin-4-PEG-DBCO, a second vial comprising a non-radiolabeled precursor of [¹⁸F]FPPEGA, e.g., 4-PEG-tosyl-azide, and optionally, a third vial comprising ¹⁸F (e.g., in O¹⁸ water). The kits may further comprise vials, solutions and optionally additional reagents necessary for the manufacture of a [¹⁸F]-PD-L1 Adnectin-4-PEG-DBCO-FPPEGA. The kits may contain instructions to complete the synthesis of the [¹⁸F]-PD-L1 Adnectin-4-PEG-DBCO-FPPEGA, per the methods described in the Examples.

Similarly, kits may comprise the reagents necessary for forming a ⁶⁴Cu labelled anti-PD-L1 Adnectin, such as the reagents described herein.

XIV. EXEMPLARY EMBODIMENTS

1. A polypeptide comprising a fibronectin type III tenth domain (¹⁰Fn3), wherein (a) the ¹⁰Fn3 domain comprises AB, BC, CD, DE, EF, and FG loops, (b) the ¹⁰Fn3 has at least one loop selected from loop BC, DE, and FG with an altered amino acid sequence relative to the sequence of the corresponding loop of the human ¹⁰Fn3 domain (SEQ ID NO: 1), and (c) the polypeptide specifically binds to PD-L1. 2. The polypeptide of embodiment 1, wherein the polypeptide binds to PD-L1 with a K_(D) of 500 mM or less. 3. The polypeptide of embodiment 2, wherein the polypeptide binds to PD-L1 with a K_(D) of 100 mM or less. 4. The polypeptide of any one of embodiments 1-3, wherein the BC, DE, and FG loops comprise the amino acid sequences of:

(a) SEQ ID NOs: 6, 7, and 8, respectively;

(b) SEQ ID NOs: 21, 22, and 23, respectively;

(c) SEQ ID NOs: 36, 37, and 38, respectively;

(d) SEQ ID NOs: 51, 52, and 53, respectively;

(e) SEQ ID NOs: 66, 67, and 68, respectively;

(f) SEQ ID NOs: 81, 82, and 83, respectively; or

(g) SEQ ID NOs: 97, 98, and 99, respectively.

5. The polypeptide of any one of embodiments 1-4, wherein the polypeptide comprises an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to SEQ ID NO: 5, 20, 35, 50, 65, 80, or 96.

6. The polypeptide of embodiment 5, wherein the polypeptide comprises an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to SEQ ID NO: 80.

7. The polypeptide of embodiment 5, wherein the polypeptide comprises an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to SEQ ID NO: 96.

8. The polypeptide of any one of embodiments 1-7, wherein the polypeptide comprises an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to the non-BC, DE, and FG loop regions of SEQ ID NO: 5, 20, 35, 50, 65, 80, or 96.

9. The polypeptide of any one of embodiments 1-7, wherein the polypeptide comprises an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to an amino acid sequence selected from the group consisting of: SEQ ID NOs: 9-15, 24-30, 39-45, 54-60, 69-75, 84-91, and 100-107. 10. The polypeptide of any one of embodiments 1-7 and 9, wherein the polypeptide comprises an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to the non-BC, DE, and FG loop regions of an amino acid sequence selected from the group consisting of: SEQ ID NOs: 9-15, 24-30, 39-45, 54-60, 69-75, 84-91, and 100-107. 11. The polypeptide of any one of embodiments 1-10, wherein the polypeptide comprises an N-terminal leader selected from the group consisting of SEQ ID NOs: 112-121, and/or a C-terminal tail selected from the group consisting of SEQ ID NOs: 122-156. 12. The polypeptide of any one of embodiments 1-11, wherein the polypeptide comprises one or more pharmacokinetic (PK) moieties selected from the group consisting of polyethylene glycol, sialic acid, Fc, Fc fragment, transferrin, serum albumin, a serum albumin binding protein, and a serum immunoglobulin binding protein. 13. The polypeptide of embodiment 12, wherein the PK moiety and the polypeptide are linked via at least one disulfide bond, a peptide bond, a polypeptide, a polymeric sugar or a polyethylene glycol moiety. 14. The polypeptide of embodiment 13, wherein the PK moiety and the polypeptide are linked via a linker with an amino acid sequence selected from the group consisting of SEQ ID NOs: 167-216. 15. A nucleic acid encoding the polypeptide of any one of embodiments 1-14. 16. The nucleic acid of embodiment 15, wherein the nucleic acid comprises a nucleotide sequence selected from the group consisting of SEQ ID NOs: 16-19, 31-34, 46-49, 61-64, 76-79, 92-95, and 108-111. 17. A vector comprising the nucleic acid of embodiment 15. 18. A cell comprising the nucleic acid of embodiment 15. 19. A composition comprising the polypeptide of any one of embodiments 1-14, and a carrier. 20. An imaging agent comprising the polypeptide of any one of embodiments 1-14, and a detectable label. 21. The imaging agent of embodiment 20, wherein the detectable label is detectable by positron emission tomography. 22. The imaging agent of embodiment 20 or 21, wherein the polypeptide is conjugated to the detectable label by an moiety selected from the group consisting of DFO, DOTA, CB-DO2A. 3p-C-DEPA, TCMC, DBCO, DIBO, BARAC, DIMAC, Oxo-DO3A, TE2A, CB-TE2A, CB-TE1A1P, CB-TE2P, MM-TE2A, DM-TE2A, diamsar, NODASA, NODAGA, NOTA, NETA, TACN-TM, DTPA, 1B4M-DTPA, CHX-A″-DTPA, TRAP, NOPO, AAZTA, DATA, H₂dedpa, H₄octapa, H₂azapa, H₅decapa, H₆phospa, HBED, SHBED, BPCA, CP256, PCTA, HEHA, PEPA, EDTA, TETA, and TRITA. 23. The imaging agent of embodiment 22, wherein the conjugating moiety is NODAGA. 24. The imaging agent of any one of embodiments 20-23, wherein the detectable label is a radionuclide. 25. The imaging agent of embodiment 24, wherein the radionuclide is selected from the group consisting of: ⁶⁴Cu, ¹²⁴I, ^(76/77)Br, ⁸⁶Y, ⁸⁹Zr, ⁶⁸Ga, ¹⁸F, ¹¹C, ¹²⁵I, ¹²⁴I, ¹³¹I, ¹²³I, ¹³¹I, ¹²³I, ³²Cl, ³³Cl, ³⁴Cl, ⁶⁸Ga, ⁷⁴Br, ⁷⁵Br, ⁷⁶Br, ⁷⁷Br, ⁷⁸Br, ⁸⁹Zr, ¹⁸⁶Re, ¹⁸⁸Re, ⁹⁰Y, ¹⁷⁷Lu, ⁹⁹Tc, or ¹⁵³Sm. 26. The imaging agent of embodiment 25, wherein the radionuclide is ¹⁸F. 27. The imaging agent of embodiment 25, wherein the radionuclide is ⁶⁴Cu. 28. The imaging agent of embodiment 24, wherein the chelating agent is NODAGA and the radionuclide is ⁶⁴Cu. 29. The imaging agent of embodiment 24, wherein the imaging agent comprises the polypeptide of embodiment 6, the NODAGA, and the radionuclide ⁶⁴Cu. 30. The imaging agent of embodiment 24, wherein the imaging agent comprises the polypeptide of embodiment 7, NODAGA, and the radionuclide ⁶⁴Cu. 31. An imaging agent comprising the polypeptide of any one of embodiments 1-14, a ¹⁸F-radiolabeled prosthetic group and a bifunctional conjugating (BFC) moiety, wherein the imaging agent has the following structure,

wherein the ¹⁸F is ortho to the N atom, x is an integer from 1 to 8, or pharmaceutically acceptable salt thereof. 32. The imaging agent of embodiment 31, wherein ¹⁸F-radiolabeled prosthetic group has the following structure,

33. The imaging agent of embodiment 31 or 32, wherein the [O(CH₂)₂]_(x) moiety is present in the 1-3 configuration relative to the nitrogen on the pyridine ring. 34. The imaging agent of embodiment 31 or 32, wherein the [O(CH₂)₂]_(x) moiety is present in the 1-2 configuration relative to the nitrogen on the pyridine ring. 35. The imaging agent of embodiment 31 or 32, wherein the [O(CH₂)₂]_(x) moiety is present in the 1-4 configuration relative to the nitrogen on the pyridine ring. 36. The imaging agent of embodiment 31, wherein ¹⁸F-radiolabeled prosthetic group has the following structure,

37. The imaging agent of any one of the embodiments 31 to 36, wherein x is an integer from 2 to 6. 38. The imaging agent of embodiment 37, wherein x is an integer from 3 to 5. 39. The imaging agent of embodiment 37, wherein x is 4. 40. The imaging agent of any one of embodiments 31-39, wherein the [O(CH₂)₂]_(x) moiety is present in the 1-3 configuration relative to the nitrogen on the pyridine ring. 41. The imaging agent of any one of the embodiments 31-40, wherein the pyridine ring comprises an additional substituent which does not interfere with the fluorination reaction. 42. The imaging agent of embodiment 41, wherein the substituent on the pyridine ring is a C₁₋₆ alkyl. 43. The imaging agent of embodiment 42, wherein the substituent is methyl, ethyl or propyl. 44. The imaging agent of embodiment 31, wherein the ¹⁸F-radiolabeled prosthetic group has the structure

45. An imaging agent comprising the polypeptide of any one of embodiments 1-14, an ¹⁸F-radiolabeled prosthetic group and a bifunctional conjugating (BFC) moiety, wherein the imaging agent has the following structure

wherein “OPEG” is [O(CH₂)₂]_(x), and x is an integer from 1 to 8, or a pharmaceutically acceptable salt thereof and wherein “Protein” is the polypeptide comprised in the imaging agent of any one of embodiments 1-14. 46. The imaging agent of embodiment 45, wherein x is an integer from 2 to 6, or a pharmaceutically acceptable salt thereof. 47. The imaging agent of embodiment 45, wherein x is an integer from 3 to 5, or a pharmaceutically acceptable salt thereof. 48. The imaging agent of embodiment 45, wherein x is 4, or a pharmaceutically acceptable salt thereof. 49. The imaging agent of any one of embodiments 31 to 48, wherein the BFC is a cyclooctyne comprising a reactive group that forms a covalent bond with an amine, carboxyl, carbonyl or thiol functional group on the protein. 50. The imaging agent of embodiment 49, wherein the cyclooctyne is selected from the group consisting of dibenzocyclooctyne (DIBO), biarylazacyclooctynone (BARAC), dimethoxyazacyclooctyne (DIMAC) and dibenzocyclooctyne (DBCO). 51. The imaging agent of embodiment 50, wherein the cyclooctyne is DBCO. 52. The imaging agent of any one of embodiments 31 to 51, wherein the BFC further comprises a polyethylene glycol (PEG)_(y) spacer arm, wherein y is an integer from 1 to 8. 53. The imaging agent of embodiment 52, wherein y is an integer from 2 to 6. 54. The imaging agent of embodiment 52, wherein y is 4 or 5. 55. The imaging agent of embodiment 52, wherein the BFC is DBCO-PEG4-NHS-Ester, DBCO-Sulfo-NHS-Ester, DBCO-PEG4-Acid, DBCO-PEG4-Amine or DBCO-PEG4-Maleimide. 56. The imaging agent of embodiment 55, wherein the BFC is DBCO-PEG4-Maleimide. 57. The imaging agent of embodiment 31, wherein the imaging agent has the structure:

wherein X is a polypeptide comprising the amino acid sequence of any one of SEQ ID NOs: 13, 28, 43, 58, 73, 88, and 104.

58. The imaging agent of embodiment 57, wherein the polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 88.

59. The imaging agent of embodiment 57, wherein the polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 104.

60. A kit comprising the polypeptide, composition, or imaging agent of any one of embodiments 1-14 and 19-59, and instructions for use.

61. A method of detecting PD-L1 in a sample comprising contacting the sample with the polypeptide of any one of embodiments 1-14, and detecting PD-L1.

62. A method of detecting PD-L1 positive cells in a subject comprising administering to the subject an imaging agent of any one of embodiments 31-59, and detecting the imaging agent, the detected imaging agent defining the location of the PD-L1 positive cells in the subject. 63. A method of detecting PD-L1-expressing tumors in a subject comprising administering to the subject an imaging agent of any one of embodiments 31-59, and detecting the imaging agent, the detected imaging agent defining the location of the tumor in the subject. 64. The method of embodiment 62 or 63, wherein the imaging agent is detected by positron emission tomography. 65. A method of obtaining an image of the imaging agent of any one of embodiments 31-59, the method comprising,

a) administering the imaging agent to a subject; and

b) imaging in vivo the distribution of the imaging agent by positron emission tomography.

66. A method of obtaining a quantitative image of tissues or cells expressing PD-L1, the method comprising contacting the cells or tissue with the imaging agent of any one of embodiments 31-59, and detecting or quantifying the tissue expressing PD-L1 using positron emission tomography. 67. A method for detecting a PD-L1-expressing tumor comprising administering an imaging-effective amount of the imaging agent of any one of embodiments 31-59 to a subject having a PD-L1-expressing tumor, and detecting the radioactive emissions of said imaging agent in the tumor using positron emission tomography, wherein the radioactive emissions are detected in the tumor. 68. A method of diagnosing the presence of a PD-L1-expressing tumor in a subject, the method comprising

(a) administering to a subject in need thereof the imaging agent of any one of embodiments 31-59; and

(b) obtaining an radio-image of at least a portion of the subject to detect the presence or absence of the imaging agent;

wherein the presence and location of the imaging agent above background is indicative of the presence and location of the disease.

69. A method of monitoring the progress of an anti-tumor therapy against PD-L1-expressing tumors in a subject, the method comprising

(a) administering to a subject in need thereof the imaging agent of any one of embodiments 31-59 at a first time point and obtaining an image of at least a portion of the subject to determine the size of the tumor;

(b) administering an anti-tumor therapy to the subject;

(c) administering to the subject the imaging agent at one or more subsequent time points and obtaining an image of at least a portion of the subject at each time point; wherein the dimension and location of the tumor at each time point is indicative of the progress of the disease.

INCORPORATION BY REFERENCE

All documents and references, including patent documents, e.g., PCT/US15/62485 and PCT/US15/62502 and websites, described herein are individually and specifically incorporated by reference herein into this document to the same extent as if there were written in this document in full or in part.

The invention is now described by reference to the following examples, which are illustrative only, and are not intended to limit the present invention. While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one of skill in the art that various changes and modifications can be made thereto without departing from the spirit and scope thereof.

EXAMPLES Example 1: Identification of PD-L1 Binding Adnectins

Anti-PD-L1 Adnectins were isolated from an Adnectin library screened with a human PD-L1 protein, or were affinity matured by PROfusion from clones identified in the library. The full length sequences, core sequences, BC, DE, and FG loop sequences of these Adnectins, as well as variants with a “PC” modified C-terminus, are presented in FIG. 1 and Table 3.

For example, the high-affinity, anti-PD-L1 Adnectin, ADX_5322_A02 (“A02”), was obtained by affinity-maturing the ATI-964 Adnectin. The gene encoding ATI-964 was re-diversified by introducing a small fraction of non-wild-type nucleotides at each nucleotide position that encoded a residue in loop BC, DE, or FG. The resulting library of Adnectin sequences related to ATI-964 was then subjected to in vitro selection by PROfusion (mRNA display) for binding to human PD-L1 under high-stringency conditions. The clones enriched after completed selection were sequenced, expressed in HTPP format, and screened for their ability to bind PD-L1 and for their fraction of monomericity. The clone with the best combination of affinity for PD-L1 and robust biophysical properties was mutated to include a C-terminal Cysteine, first with the C-terminal sequence NYRTPCH6 (the form identified as ADX_5322_A02), and later with the C-terminal sequence NYRTPC.

The same process was followed to affinity-mature ATI-967, resulting in the Adnectin ADX_5417_E01. Similarly, affinity matured ATI_1760_C02, ATI_1760_E01 (“E01”) and ATI_1760_F01 were obtained by affinity maturation of ATI_1422_G05.

Additional anti-human PD-L1 adnectins were isolated. Their sequences are set forth in Table 3.

Expression and Purification of His-Tagged Anti-PD-L1 Adnectins

All DNA constructs contained an N-terminal his tag followed by a TVMV recognition sequence. The expression plasmids (pET-28 NM vector) for the anti-PD-L1 Adnectins described supra were transformed into BL21(DE3) cells (New England Biolabs). Cells were grown in Overnight Express Autoinduction media (Novagen) in 1 L shake flasks at 37° C. for 6 hours followed by 20° C. for 16 hours at 220 RPM. Cells were harvested by centrifugation and suspended in PBS pH 7.2. Cells were lysed mechanically, then clarified by centrifugation. Soluble fractions were bound by gravity feed to Ni-NTA Agarose resin (Qiagen), washed in 20 mM Tris+10 mM Imidazole pH 8.0, followed by 20 mM Tris+40 mM Imidazole pH 8.0, and eluted with 20 mM Tris+400 mM Imidazole pH 8.0. Nickel eluates were spiked with TVMV protease at 1:23-fold molar excess of Adnectin. The TVMV-Adnectin eluate mixtures were dialyzed against 20 mM Tris pH 8.0 at 4° C. for 16 hours. To separate the TVMV protease and cleaved his tag fragments, samples were loaded onto a 10 mL HisTrap FF column (GE Healthcare) and flow through fractions were collected.

Example 2: Biophysical Assessment of PD-L1 Adnectins

The binding properties of ATI-1420D05, ATI-1420D05, ATI-1421E04 and ATI-1422G05, ATI_1760_C02, ATI_1760_E01 and ATI_1760_E01 were assessed.

TABLE 1 Binding properties of anti-PD-L1 Adnectins Sequence Name SEQ ID K_(D)(nM) ATI-1420B09 2.5 ATI-1420D05 9.5 AT1-1421E04 5.6

Binding properties of the purified ATI-964, ATI-967, ATI-968, ADX_5322_A02, and ADX_5417_E01 Adnectins to human or cyno PD-L1, as determined by Biacore, are shown in Table 2. Cell binding was determined by measuring binding to human PD-L1 positive cells L2987.

TABLE 2 Biophysical properties of anti-PD-L1 Adnectins Melting Transition Cell Binding Kinetics Midpoint Binding SEQ K_(D) (M) for (Tm)° C. EC₅₀ Sequence Name ID k_(a) (1/Ms) k_(d) (s) K_(D) (M) cynoPD-L1 N.D. N.D. ATI-964 30 3.6 × 10⁵ 7.7 × 10⁻⁵ 2.1 × 10⁻¹⁰ 1.4 × 10⁻¹⁰ N.D. 4.4 ATI-965 45 4.6 × 10⁵ 3.3 × 10⁻⁴ 7.1 × 10⁻¹⁰  8 × 10⁻¹⁰ N.D. 4.9 ATI-966 60 2.5 × 10⁶ 6.9 × 10⁻⁵ 2.8 × 10⁻¹¹ 3.8 × 10⁻¹¹ N.D. 2.3 ATI-967 75 2.1 × 10⁶ 6.7 × 10⁻⁵ 3.2 × 10⁻¹¹  6 × 10⁻¹¹ N.D. N.D. ATI-968 15 7.5 × 10⁵ 1.2 × 10⁻⁴ 1.6 × 10⁻¹⁰ 1.1 × 10⁻¹⁰ 60 3.4 ADX_5322_A02 91 2.5 × 10⁶ 5.7 × 10⁻⁴ 2.28 × 10−¹⁰  N.D. 82 0.43 nM (Cys-Capped) ADX_5417_E01 107 2.0 × 10⁷ 2.6 × 10⁻⁴  1.3 × 10−¹¹ N.D. 73 N.D.

The binding data indicates that the affinity matured anti-human PD-L1 adnectins bind to human PD-L1 with affinities that are less than 1 nM or even less than 0.1 nM. Exemplary inhibition curves are shown in FIG. 12.

Anti-PD-L1 adnectins have the following additional characteristics:

-   -   Inhibiting the binding of human PD-1 to human PD-L1, as         determined by measuring inhibition of binding of human PD-1Fc to         the PD-L1 positive cells L2987 by flow cytometry, and shown,         e.g., for adnectins ATI-964, ATI-965, ATI-966, ATI-967, ATI-968,         A02 and E01;     -   Inhibiting the binding of human CD80 (B7-1) to human PD-L1, as         determined by ELISA. For example, ATI-964 inhibits binding with         an EC50 of 41 pM; ATI-965 inhibits binding with an EC50 of 210         pM; ATI-966 inhibits binding with an EC50 of 28 pM; and ATI-968         inhibits binding with an EC50 of 56 pM;     -   Inhibiting the binding of the anti-PD-L1 antibody 12A4 to human         PD-L1, as determined by ELISA.

Anti-PD-L1 antibodies were also tested in a mixed lymphocyte reaction (MLR): ATI-964, ATI-965, and ATI-968 were active in an MLR, whereas ATI-966 and ATI-967 were not active in an MLR.

The following examples relate to the labeling of anti-PD-L1 Adnectins with ¹⁸F and ⁶⁴Cu.

Example 3: Preparation of 2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethyl 4-methylbenzenesulfonate

A mixture of ((oxybis(ethane-2,1-diyl))bis(oxy))bis(ethane-2,1-diyl) bis(4-methylbenzenesulfonate) (5 g, 9.95 mmol) and sodium azide (0.647 g, 9.95 mmol) were dissolved in ethanol (50 mL) and the reaction was refluxed at 90° C. over a 17 hour period. The solvent was removed using partial vacuum and then loaded onto a 40 gram silica cartridge and purified using flash chromatography (IscoCombiFlash—eluted using a linear gradient method starting from 10% ethyl acetate in hexanes going to a 90% ethyl acetate in hexanes over a 45 minute period). The pooled fractions were checked by TLC and combined to give 2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethyl 4-methylbenzenesulfonate as a colorless oil. Due to the reactive nature of the 2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethyl 4-methylbenzenesulfonate product this material was used “as is” without any further characterizations.

Example 4: Preparation of 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine

To a suspension of sodium hydride (0.129 g, 3.21 mmol) in DMF (10 mL) at 0° C. was dropwise added a stirring solution of 2-fluoropyridin-3-ol (0.363 g, 3.21 mmol) in DMF (5 mL), then followed by the dropwise addition of the solution of 2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethyl 4-methylbenzenesulfonate (1.00 g, 2.68 mmol) in DMF (5 mL). The suspension was held at 0° C. for 10 min, then brought to ambient temperature for 1 hour, followed by additional heating at 60° C. for 4 hours. The solvent was removed in vacuo. 100 ml of ethyl acetate was added followed by 3 separate wash extractions with concentrated brine solution. The organic layer was dried over sodium sulfate, filtered, and concentrated. The crude material was purified using flash chromatography (IscoCombiFlash—eluted with 10-50% EtOAc in Hex) to give a colorless oil. 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine (702 mg, 2.233 mmol, 83% yield) was isolated as a clear oil. ¹H NMR (400 MHz, CHLOROFORM-d) δ 7.75 (dt, J=4.9, 1.6 Hz, 1H), 7.33 (ddd, J=10.0, 8.1, 1.5 Hz, 1H), 7.10 (ddd, J=7.9, 4.9, 0.7 Hz, 1H), 4.30-4.16 (m, 2H), 3.95-3.83 (m, 2H), 3.80-3.61 (m, 10H), 3.38 (t, J=5.1 Hz, 2H) 13C NMR (101 MHz, CHLOROFORM-d) δ 142.3, 137.7, 137.5, 123.4, 123.4, 121.7, 121.6, 77.3, 76.7, 70.9, 70.7, 70.6, 70.0, 69.4, 69.0, 50.6 19F NMR (400 MHz, CHLOROFORM-d) 6-83.55. HRMS (ESI) Theory: C13H20FN4O4+m/z 315.464; found 315.1463.

Example 5: Preparation of 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-nitropyridine

Sodium hydride (0.121 g, 3.01 mmol) (60% suspension in oil) was dissolved in DMF (7.0 mL) and the resulting suspension was cooled to 0° C. A solution of 2-nitropyridin-3-ol (0.384 g, 2.74 mmol) in DMF (1.5 mL) was added slowly, followed by the dropwise addition of 2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethyl 4-methylbenzenesulfonate (1.023 g, 2.74 mmol) in DMF (1.5 mL). The suspension was held at 0° C. for 10 minutes, then brought to ambient temperature for 2 hours followed by heating 60° C. for a 72 hour period. The reaction was quenched with 10 ml of DI water, followed by ethyl acetate extraction (3×10 mL). Pooled EtOAc extracts were washed with a concentrated brine solution (10 mL), dried over sodium sulfate, filtered, and evaporated under reduced pressure to give a light yellow oil. The crude was purified by flash chromatography. 24 g silica cartridge, 25 mL/min, starting from 10% ethyl acetate in hexanes, followed by a linear change to 50% ethyl acetate in hexanes over a 25 minute period. After this time, the gradient was held at this solvent composition for 10 minutes then changed to 100% ethyl acetate over a 10 minute period. 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-nitropyridine was eluted between the 30-40 minute portion of the chromatogram and the pooled fractions were evaporated under reduced pressure, then under vacuum for 2 hours to give 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-nitropyridine (687 mg, 1.973 mmol, 72.0% yield) as a light yellow oil. ¹H NMR (400 MHz, CHLOROFORM-d) δ 8.11 (dt, J=4.9, 1.6 Hz, 1H), 7.60 (ddd, J=10.0, 8.1, 1.5 Hz, 1H), 7.52 (ddd, J=7.9, 4.9, 0.7 Hz, 1H), 4.30-4.16 (m, 2H), 3.95-3.83 (m, 2H), 3.80-3.61 (m, 10H), 3.38 (t, J=5.1 Hz, 2H) 13C NMR (101 MHz, CHLOROFORM-d) δ 147.3, 139.5, 128.4, 124.4, 71.1, 70.7, 70.6, 70.0, 69.9, 69.3, 50.7. HRMS (ESI) Theory: C13H20N5O6+m/z 342.1408; found 342.1409

Example 6: Synthesis of 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-bromopyridine

To the suspension of sodium hydride (NaH, 25.7 mg, 0.643 mmol) in dimethylformamide (DMF, 5 mL) at 0° C. was dropwise added a solution of 2-bromopyridin-3-ol (112 mg, 0.643 mmol) in DMF (1 mL), followed by the dropwise addition of the solution of 2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethyl 4-methylbenzenesulfonate (200 mg, 0.536 mmol) in DMF (1 mL). The suspension was held at 0° C. for 10 minutes, then brought to ambient temperature and held for 1 hour, followed by heating to 60° C. for 4 hours. Upon completion of heating, the solvent of the crude reaction mixture was removed in vacuo. The crude reaction was reconstituted in 50 mL of ethyl acetate, washed with 2×50 mL of a aqueous brine solution, and the organic layer was dried over magnesium sulfate, filtered, and concentrated in vacuo. The crude reaction was purified using reverse-phase HPLC to give 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-bromopyridine, TFA (112 mg, 0.229 mmol, 42.7% yield) as a light yellow oil. HRMS ESI m/z (M+H), Theory C13H20BrN4O4 375.0664 found 375.0662; ¹H NMR (400 MHz, DMSO-d₆) δ 7.97 (dd, J=4.6, 1.5 Hz, 1H), 7.54 (dd, J=8.2, 1.6 Hz, 1H), 7.40 (dd, J=8.1, 4.6 Hz, 1H), 4.24 (dd, J=5.3, 3.9 Hz, 2H), 3.85-3.78 (m, 2H), 3.68-3.62 (m, 2H), 3.62-3.52 (m, 8H), 3.42-3.34 (m, 2H).

Example 7: Scheme for Synthesis of Trimethylanilium Compound

Example 8: Synthesis of 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-N,N-dimethylpyridin-2-amine

A mixture of 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine (160 mg, 0.509 mmol), potassium carbonate (K₂CO₃, 84 mg, 0.611 mmol), and dimethylamine (40% in water, 0.097 mL, 0.764 mmol) in dimethylsulfoxide (DMSO, 2.5 mL) were heated in a sealed pressure-proof vessel at 110° C. for 14 hours. Upon completion of heating, the solvent of the crude reaction mixture was removed in vacuo. The crude reaction was reconstituted in 50 mL of ethyl acetate, washed with 2×50 mL of a aqueous brine solution, and the organic layer was dried over magnesium sulfate, filtered, and concentrated in vacuo. The crude reaction was purified using normal-phase chromatography to give 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-N,N-dimethylpyridin-2-amine (140 mg, 0.413 mmol, 81% yield) as a colorless oil. ¹H NMR (400 MHz, CHLOROFORM-d) δ 7.86 (dd, J=4.9, 1.5 Hz, 1H), 7.02 (dd, J=7.8, 1.5 Hz, 1H), 6.73 (dd, J=7.8, 4.9 Hz, 1H), 4.20-4.07 (m, 2H), 3.98-3.86 (m, 2H), 3.81-3.61 (m, 9H), 3.38 (t, J=5.1 Hz, 2H), 3.13-2.94 (m, 6H), 1.69 (s, 2H). HRMS (ESI) Theory: C15H26N5O4+m/z 340.1980; found 340.1979.

Example 9: Synthesis of 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-N,N,N-trimethylpyridin-2-aminium

Methyl trifluoromethanesufonate (0.065 mL, 0.589 mmol) was added to the solution of 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-N,N-dimethylpyridin-2-amine (40 mg, 0.118 mmol) in toluene (1.5 mL) in a sealed container under a steady stream of nitrogen. The reaction mixture was stirred at room temperature over a 14 hour period. The solvent was removed and the resultant residue was washed with 2×10 ml of ether, azeotropically dried with 2×1 ml of dichloromethane, and dried under high-pressure vacuum overnight to give 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-N,N,N-trimethylpyridin-2-aminium, trifluoromethanesulfonate salt in quantitative yield as a thick colorless oil. LCMS m/z 354.33; ¹H NMR (400 MHz, DMSO-d₆) δ 8.24-8.17 (m, 1H), 7.98 (d, J=8.3 Hz, 1H), 7.75 (ddd, J=8.2, 4.6, 3.2 Hz, 1H), 4.44 (br. s., 2H), 3.88 (d, J=3.9 Hz, 2H), 3.69-3.45 (m, 21H).

Example 10: Synthesis of [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine Using 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-N,N,N-trimethylpyridin-2-aminium, Trifluoromethanesulfonate Salt

An aqueous [¹⁸F]-Fluoride solution (2.0 ml, 33.3 GBq/900 mCi) was purchased from P.E.T. Net® Pharmaceuticals in West Point Pa. and directly transferred to a Sep-Pak light QMA [The Sep-Pak light QMA cartridge was pre-conditioned sequentially with 5 ml of 0.5 M potassium bicarbonate, 5 ml of deionized water, and 5 ml of MeCN before use.] Upon completion of this transfer, the aqueous [¹⁸F] fluoride was released from the QMA Sep-Pak by the sequential addition of potassium carbonate (15 mg/ml; 0.1 ml) followed by a mixture of potassium carbonate (30 mg/ml, 0.1 ml), 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (15 mg, 0.04 mmol) and 1.2 ml of MeCN. The solvent was evaporated under a gentle stream of nitrogen at 90° C. and vacuum. Azeotropic drying was repeated twice with 1 ml portions of acetonitrile to generate the anhydrous K.2.2.2/K[¹⁸F]F complex. 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-N,N,N-trimethylpyridin-2-aminium, trifluoromethanesulfonate salt (2 mg, 5.6 μmol) was dissolved in 500 microliters of DMSO and added to the dried cryptand. This solution was heated at 120° C. for 10 minutes. After this time, the crude reaction mixture was diluted with 3 ml of DI water. The entire contents of the crude reaction mixture was then transferred, loaded, and purified using reverse phase HPLC under the following conditions: HPLC Column: Luna C18 250×10 Solvent A: 0.1% TFA in DI water; solvent B: 0.1% TFA in acetonitrile at a flow rate of 4.6 ml/minute using isocratic method 32% B while the UV was monitored at 280 nm. [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine was isolated at the 24 min mark of the chromatogram and collect over a 2 minute period. This product was collected into a 100 ml flask that contained 10 ml of DI water and the entire contents were delivered to a Sep-Pak Vac tC18 6 cc 1 g sep pack from Waters. 6.1 GBq/164 mCi of [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine was isolated from this reaction. This was released from the sep-pak using 3 ml of ethanol and this solution was reduced with 98° C. heat source, a gentle stream of nitrogen, and vacuum over a 15 minute period until only a film remained in the vial. The final product was reconstituted in 100% 1×PBS buffer and was stable in this media for over 1 hour at 37° C.

The [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine may be used to generate ¹⁸F-labeled biologic products (e.g., ¹⁸F-labeled anti-PD-L1 Adnectins, as described below) by taking advantage of “click” azide-alkyne reaction with the appropriate biologic containing an alkynes.

Example 11: Production of ¹⁸F-Radiolabeled Protein Using “Click Chemistry”

A. Fluorination of the 4-PEG-Tosyl-Azide Precursor to Form [¹⁸F]-FPPEGA

900 mCi of ¹⁸F in ¹⁸O water (3 ml) activity (purchased from IBA Molecular) was transferred directly into a micro vial (no QMA) that contained 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (2.8 mg, 7.44 μmol) and potassium carbonate (1.7 mg, 0.012 mmol). An additional 2.0 ml of acetonitrile was transferred into this crude reaction mixture and the entire mixture was azeotropically dried. This was completed by evaporating the solution using a 98° C. oil bath, and applying a gentle stream of N₂ and partial vacuum. The solution's volume was reduced to about 2 ml. An additional 2 ml of acetonitrile was added and the process was repeated 3 times over a 40 minute period. When the volume of the liquid was reduced to less than 0.3 ml, a 0.7 ml aliquot of acetonitrile was added and the solution reduced by further azeotropic distillation until the volume was ˜0.1 ml. An additional 0.9 ml of acetonitrile was added and this process was completed until a white solid was formed. This process took ˜55 minutes. During the final procedure, the vial was removed from the oil bath before the solution had gone to dryness and the residue in the vial was placed under full vacuum (no N₂ flow) at room temperature for 20 minutes. Total time for transfer and drying of cryptand mixture was 65 min.

To the dried cryptand mixture was added 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-nitropyridine (2 mg, 5.86 μmol) dissolved in 500 microliters of DMSO and this mixture was heated at 120° C. for 10 minutes. After this time the crude reaction mixture was diluted with 3 ml of DI water and the entire contents were then transferred and loaded onto the following HPLC column and conditions: HPLC Column: Luna C18 250×10 mm; Solvent A: 0.1% TFA in DI water; Solvent B: 0.1% TFA in acetonitrile; flow rate 4.6 ml/min; pressure 1820 PSI; isocratic method 32% B; UV—280 nm. The [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine ([¹⁸F]-FPPEGA) product was isolated at the 24 minute mark of the chromatogram and was collect over a 2 minute period. This product was collected into a 100 ml flask that contained 15 ml of DI water and the entire contents were delivered to a Sep PakVac tC18 6 cc 1 g sep pack. PN WAT036795. The [¹⁸F]-FPPEGA was released from the Sep Pak using 2.5 ml of ethanol and this solution was reduced with 98° C. N₂ and vacuum over a 15 minute period until dryness. This compound was dissolved in 0.1 ml 1×PBS (phosphate buffered saline). This product was analyzed using a Varian HPLC HPLC Column Luna C18 (2) 4.6×150 mm Solvent A: 0.1% TFA in DI water; Solvent B: 0.1% TFA in acetonitrile; flow rate 1.0 ml/min; gradient method 0 min 90% A 10% B; 15 mins 30% A 70% B; 17 mins 30% A 70% B; 18 mins 90% A 10% B; 20 mins 90% A 10% B; UV—280 nm. 220 mCi of [¹⁸F]-FPPEGA was isolated.

B. Preparation of E01-4PEG-DBCO

This Example describes the linking of the E01 anti-PD-L1 Adnectin to PEG4-DBCO.

As maleimide chemistry is used to link the Adnectin to PEG4-DBCO, the E01 Adnectin was first modified by adding a proline followed by a cysteine at its C-terminus. The amino acid sequence of this modified E01 Adnectin is provided in SEQ ID NO: 104. The cysteine is used to link the Adnectin to PEG4-DBCO.

A 4-fold molar excess of Maleimide-PEG4-DBCO (Click Chemistry Tools) was dissolved in DMSO and added to the purified modified E01 Adnectin in the presence of 1 mM TCEP. Final DMSO concentrations did not exceed 5% in the conjugation mixtures. The conjugation mixture was left at room temperature for one hour before mass spec analysis. After MS confirmation of conjugation, the sample was purified by size-exclusion chromatography using a HiLoad 26/60 Superdex 75 column (GE Healthcare) equilibrated in PBS pH 7.2.

C. Coupling of [¹⁸F]-FPPEGA to Adnectin

A schematic for synthesizing [¹⁸F]-E01-4PEG-DBCO-FPPEGA is shown in FIGS. 2 and 9.

0.2 ml of a 5.4 mg/ml solution of the E01-4PEG-DBCO Adnectin solution (prepared as described in Section B) was incubated with 200 mCi of 0.1 ml of [¹⁸F]-FPPEGA (Example 4) in 1×PBS buffer. The solution was gently mixed by pipetting the crude reaction up and down several times and was incubated together for 45 minutes at 45° C. or room temperature. The contents of this crude reaction mixture were purified using a SEC column. Superdex 200 0.5 ml/min 1×PBS buffer and the [¹⁸F]-E01-4PEG-DBCO-FPPEGA product was isolated at the 37 min mark of the chromatogram over a 2 minute period.

[¹⁸F]-E01-4PEG-DBCO-FPPEGA was analyzed via SEC with co-injection of non-radioactive standard, RP HPLC using a PLRPS column and gel electrophoresis.

Size Exclusion Chromatography (SEC) was performed with the following parameters:

Superdex 200 column; Solvent 100% 1×PBS buffer; 0.5 ml/min 280 UV;

Reverse phase HPLC

Column: PLRPS 8 micron 1000 A 4.6×250 mm

Solvent A: 0.1% formic acid in DI water

Solvent B: Acetonitrile

Flow rate: 1 ml/min

Pressure: 1351 PSI

Gradient:

-   -   0 min 90% A 10% B     -   30 min 45% A 55% B     -   32 min 25% A 75% B     -   36 min 25% A 75% B     -   50 min 90% A 10% B

15 mCi [¹⁸F]-E01-4PEG-DBCO-FPPEGA was isolated with a radiochemical purity (RCP) of >99% via both SEC and RP HPLC calculations, and with a specific activity of 0.6 mCi/nmol, when the reaction was conducted at 45° C. When conducting the reaction at room temperature, 5.72 mCi was obtained. Specific activity of the [¹⁸F]-FPPEGA was 0.512 mCi/nmol and RCP of 85.7% 3 hours post the end of its synthesis, when conducting the reaction at 45° C. or at room temperature, respectively. Specific activity was measured via Nanodrop (see, www.nanodrop.com). The product co-eluted with non-radioactive standard on both SEC and PLRPS. Gel electrophoresis confirmed an ¹⁸F product consistent with an 11 kDa molecular weight standard.

The ¹⁸F-radiolabeled E01-4PEG-DBCO can be used in a variety of in vitro and/or in vivo imaging applications, including diagnostic imaging, basic research, and radiotherapeutic applications. Specific examples of possible diagnostic imaging and radiotherapeutic applications, include determining the location, the relative activity and/or quantifying of PD-L1 positive tumors, radioimmunoassay of PD-L1 positive tumors, and autoradiography to determine the distribution of PD-L1 positive tumors in a mammal or an organ or tissue sample thereof.

In particular, the ¹⁸F-radiolabeled E01-4PEG-DBCO is useful for positron emission tomographic (PET) imaging of PD-L1 positive tumors in the lung, heart, kidneys, liver and skin and other organs of humans and experimental animals. PET imaging using the ¹⁸F-radiolabeled E01-4PEG-DBCO can be used to obtain the following information: relationship between level of tissue occupancy by candidate PD-L1 tumor-treating medicaments and clinical efficacy in patients; dose selection for clinical trials of PD-L1 tumor-treating medicaments prior to initiation of long term clinical studies; comparative potencies of structurally novel PD-L1 tumor-treating medicaments; investigating the influence of PD-L1 tumor-treating medicaments on in vivo transporter affinity and density during the treatment of clinical targets with PD-L1 tumor-treating medicaments; changes in the density and distribution of PD-L1 positive tumors during effective and ineffective treatment.

D. Alternative Method for Preparing ¹⁸F Labeled Adnectins

A slightly altered method for synthesizing [18F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine and labelling Adnectins therewith is provided.

900 mCi of Fluorine-18 in ¹⁸O water (2 ml) activity was purchased from IBA molecular and delivered into the remote controlled synthesis unit. This sample was transferred directly into a micro vial that contained 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (3.2 mg, 8.50 μmol) and potassium carbonate (1.4 mg, 10.13 μmol). An additional 1.5 ml of acetonitrile was transferred into this vial and the entire mixture was azeotropically dried. This solution was then evaporated by placing the vial into a 90° C. oil bath and applying a gentle stream of N₂ and partial vacuum. This was completed by first using partial vacuum for 10 minutes while heating. The total volume of the microvial was reduced to about 2 ml. An additional 2 ml of acetonitrile was added and this process was repeated 3 times over a 40 minute period. When the volume of the liquid was reduced to less than 0.3 ml, 0.7 ml aliquot of acetonitrile was added and the solution reduced by azeotropic distillation until the volume was ˜0.1 ml, and additional 0.9 MeCN was added and this process was completed until a white solid was formed. During the final procedure, the vial was removed from the oil bath before the solution had gone to dryness and the residue in the vial was placed under full vacuum at room temperature for 20 minutes. 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-nitropyridine (2 mg, 5.86 μmol) was dissolved in 500 microliters of DMSO and added to the dried cryptand. This solution was heated at 120° C. for 10 minutes. After this, the crude reaction mixture was diluted with 3 ml of DI water. The entire contents of the crude reaction mixture was then transferred, loaded and purified using reverse phase HPLC and the following conditions: HPLC Column: Luna C18 250×10 Solvent A: 0.1% TFA in DI water; solvent B: 0.1% TFA in acetonitrile at a flow rate of 4.6 ml/minute using isocratic method 32% B while the UV was monitored at 280 nm. [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine was isolated at the 24 min mark of the chromatogram and was collected over a 2 minute period. This product was collected into a 100 ml flask that contained 10 ml of DI water and the entire contents were delivered to a Sep-Pak Vac tC18 6 cc 1 g sep pack from Waters. 224 mCi of [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine was isolated from this reaction. This was released from the sep-pak using 3 ml of ethanol and this solution was reduced with 98° C. heat source, a gentle stream of nitrogen, and vacuum over a 15 minute period until only a film remained in this vial. The final product was reconstituted in 100% 1×PBS buffer and is stable in this media for over 1 hour at 37 C. Using [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine generated several F-18 labeled biologic products by taking advantage of “click” azide-alkyne reaction with the appropriate biologic containing an alkyne.

Example 12: Linking of PD-L1 Adnectins to NODAGA to Generate NODAGA-PD-L1 Adnectins

This Example describes the linking of the E01 and A02 anti-PD-L1 Adnectins to NODAGA. As maleimide chemistry is used to link the Adnectins to NODAGA, both Adnectins used a proline followed by a cysteine at their C-terminus (as described for E01 above). The amino acid sequences of the modified E01 and A02 Adnectins are provided in SEQ ID NOs: 104 and 88, respectively. The cysteine will be used for linking the Adnectins to NODAGA. For ⁶⁴Cu labeling of the Adnectins, a 50-fold molar excess of maleimide-NODAGA (CheMatech) was dissolved in PBS pH 7.4 and added to the purified Adnectins in the presence of 1 mM TCEP. Final DMSO concentrations did not exceed 5% in the conjugation mixtures. Conjugation mixtures were left at room temperature for one hour before mass spec analysis. After MS confirmation of conjugation, the samples were purified by size-exclusion chromatography using a HiLoad 26/60 Superdex 75 column (GE Healthcare) equilibrated in PBS pH 7.2.

Example 13: Synthesis of ⁶⁴Cu-Based Anti-PD-L1 Adnectin Probes

Synthesis of ⁶⁴Cu-A02-NODAGA

[⁶⁴Cu]-Copper chloride (⁶⁴CuCl₂) in 0.1N hydrochloric acid solution was neutralized with 0.8 mL of 0.1N sodium acetate (NaOAc) aqueous solution for 4 minutes at ambient temperature. 1 mL of the ⁶⁴Cu/NaOAc solution was added to A02-NODAGA (30 μL of 1.6 mg/mL) and the crude reaction was gently pippetted to allow mixing followed by resting at ambient temperature for 30 minutes. The contents of crude reaction mixture were transferred to a PD-10 desalting column that was pre-activated with 20 mL of 1× phosphate buffered saline (PBS, pH 7.4) buffer prior to loading of sample. An additional 1.5 mL of 1×PBS was added to the column, followed by an additional 0.8 ml 1×PBS solution and these fractions were discarded. [⁶⁴Cu]-A02-NODAGA was then collected after a 1.2 mL elution of the PD-10 column to give 10.79 mCi as the desired product. Quality control was measured using a reverse phase HPLC system using an Agilent PLRP-S HPLC column Size: 250×4.60 mm, 8 μm, 280 nm and a mobile phase of 0.1% Formic Acid in distilled water and acetonitrile. A gradient method was used where the percentage of acetonitrile was increased linearly from 10% to 45% over a 30 minute time frame. [⁶⁴Cu]-A02-NODAGA co-eluted with reference standard at the 22 minute mark of the HPLC chromatogram. Radiochemical purity was measured to be 96% using this method. [⁶⁴Cu]-A02-NODAGA also co-eluted with reference material at the 20 minute mark using a size exclusion chromatography, (SEC) Column: GE Superdex 200 GL Size: 10×300 mm, 280 nm. The calculated specific activity was 956.8 mCi/μmol based on Nanodrop protein concentration and isolated radioactivity of the purified sample.

Procedure for the Synthesis of ⁶⁴Cu-E01-NODAGA

[⁶⁴Cu]-Copper chloride ([⁶⁴Cu]CuCl₂) in 0.1N hydrochloric acid solution (20 mCi in 0.25 mL) was pH adjusted with 1.10 mL of 0.1N ammonium acetate buffer, then mixed and incubated with E01-NODAGA Adnectin in a 1×PBS aqueous solution (40 μL of 1.2 mg/mL, 4.62 nmol) for 30 minutes at ambient temperature. After 30 minutes of incubation, the reaction mixture (˜1250 μL) was transferred to the PD-10 desalting column (GE Healthcare Life Science, Sephadex G25 Medium, 14.5×50 mm—equilibrated with 40 mL of 1×PBS), and the sample was allowed to enter the column completely by gravity and followed with 1.1 mL of 1×PBS. After the liquid completely passed through the column, the product was collected via elution in 1 mL increments with 1×PBS per sample vial. The ⁶⁴Cu-E01-NODAGA was isolated in the second 1 ml fraction and measured to be 9.26 mCi in 1 ml of 1×PBS. This sample was analyzed using an analytical size exclusion HPLC method using an Agilent HPLC system equipped with a UV/vis detector (λ=280 nm), a posi-ram detector and Superdex 200 10/300 GL size-exclusion column (GE Healthecare Life Science, pore size 13 μm). The flow rate was 0.5 mL/min, and the aqueous mobile phase was isocratic with 1×PBS with 0.02% NaN₃ for 60 minutes. The radiochemical purity was 99% using this system, and the product co-eluted with non-radioactive reference standard. Specific activity was calculated based on the equation of the 3-points calibratio curve (y=656978x). About 100 μL of the product solution from vial 3 was injected onto the Superdex −200 size exclusion column. Product peak was collected and measured to be 0.74 mCi, UV counts of product peak was 156367 unit, and specific activity was 3.1 mCi/nmol.

Example 14: In Vitro Differentiation of PD-L1-Positive Cells from PD-L1-Negative Cells with an Anti-PD-L1 Adnectin Imaging Agent

In this experiment, the ⁶⁴Cu-E01 anti-PD-L1 Adnectin (NODAGA was used as a chelator) was tested for its ability to discriminate between hPD-L1-positive cells and hPD-L1-negative cells in vitro. Cell labeling was specific, as evidenced by differential association of ⁶⁴Cu-E01 with hPD-L1-positive L2987 cells compared to hPD-L1-negative HT-29 cells (cell associated radioactivity was 44.6× higher in hPD-L1-positive L2987 cells). Specificity was further confirmed as evidenced by a marked reduction in cell-associated ⁶⁴Cu-E01 when co-incubated with excess 450 nM cold (unlabeled) E01 Adnectin (99.6% reduction). Cell associated ¹⁸F-E01 was minimally reduced (9.9% reduction, not significant) when cells were co-incubated with 450 nM of a cold (unlabeled) non-PD-L1 binding Adnectin (FIG. 3).

1×10⁶ hPD-L1-positive L2987 human lung carcinoma cells or hPD-L1-negative HT-29 human colorectal adenocarcinoma cells were placed into 5 mL culture tubes (n=3 tubes per condition). ⁶⁴Cu-E01 Adnectin solution was prepared in PBS+0.5% BSA at a concentration of 300 nCi/200 μL. Portions of this solution were supplemented with either cold (unlabeled) E01 Adnectin or cold (unlabeled) non-PD-L1 binding Adnectin to a final concentration of 450 nM. Cell samples were centrifuged for 5 min at 200×g and then resuspended in 200 μL of the appropriate ⁶⁴Cu-E01 Adnectin solution and incubated on ice for 1 hour. After the incubation period, cell samples were centrifuged at 200×g and the supernatant was discarded. Cell pellets were resuspended in 1 mL PBS+0.5% BSA and the wash procedure repeated for a total of 3 washes. Following the final wash, cells were again centrifuged at 200×g and the supernatant was discarded. The radioactivity of the remaining cell pellets was then measured by gamma counter.

Taken together, these results demonstrate the ability of the ⁶⁴Cu-E01 Adnectin to differentiate PD-L1(+) vs. PD-L1(−) cells in vitro. Specificity was further demonstrated by a marked reduction in cell-associated radiotracer in samples co-incubated with 450 nM unlabeled anti-PD-L1 E01 Adnectin (and only a statistically insignificant reduction when co-incubated with 450 nM of a non-PD-L1 binding Adnectin). Similar experiments using different Adnectin variants as well as ¹⁸F as the radionuclide were conducted, with similar results.

Example 15: Distinguishing PD-L1-Positive Tumors from PD-L1-Negative Tumors with an Anti-PD-L1 Adnectin Imaging Agent

For PET imaging, rapid blood clearance rates provide an advantage over more slowly clearing proteins, such as antibodies, by minimizing the amount of time needed for “background” probe signals to deplete from non-relevant tissue. In the clinic, long blood half-life antibody-based-PET tracers may require several days of waiting post injection before images can be collected. Rapid clearing probes open the door to high contrast images that can be collected on the same day the probe is injected, and very importantly, they can also serve to reduce overall radiation exposure to the animals studied or patients examined.

In this experiment, the ⁶⁴Cu-A01 anti-PD-L1 Adnectin (NODAGA was used as the chelator), produced as described in the above Examples, was tested for its ability to discriminate between hPD-L1-positive tumors and hPD-L1-negative tumors in mice.

Mice bearing bilateral xenograft tumors were produced by introducing 1×10⁶ hPD-L1(+) L2987 human lung carcinoma cells and 1.5×10⁶ hPD-L1(−) HT-29 human colon carcinoma cells subcutaneously on opposite sides of the mouse. Once tumors reached approximately 300 mm³ (approximately 2-3 weeks after cell implantation), animals were selected for imaging. For imaging, animals were placed under anesthesia with 2% isoflurane and tail vein catheters were installed. Mice were then placed into a custom animal holder with capacity for 4 animals, where they remained under anesthesia for the duration of the study. The animal holder was transferred to the microPET® F120™ scanner (Siemens Preclinical Solutions, Knoxville, Tenn.). The axial field of view of this instrument is 7.6 cm. With this limitation, animals were positioned such that the scanning region was from immediately in front of the eyes to approximately the base of the tail.

A 10-minute transmission image was first acquired using a ⁵⁷Co point source for the purpose of attenuation correction of the final PET images. Following the transmission scan, radiotracer solutions were administered via the previously installed tail vein catheters and a 2 hour emission image was acquired. Injected radiotracer solutions consisted of either approximately 200 μCi ⁶⁴Cu-A02 (with a NODAGA chelator) or 200 μCi ⁶⁴Cu-A02 supplemented with 3 mg/kg final concentration of cold, unlabeled A02 Adnectin (based on individual animal weight). All injections were formulated in 200 μL saline prior to injection. Exact injected doses were calculated by taking direct measurements of the formulated dose and subtracting the radioactivity remaining in the syringe and the tail vein catheter.

Images were reconstructed using a maximum a posteriori (MAP) algorithm with attenuation correction using the collected transmission images and corrected for radioisotope decay. In the final images, regions of interest (ROIs) were drawn around the tumor boundary using ASIPro software (Siemens Preclinical Solutions). Time-activity curves were calculated for each ROI to yield a quantitative view of radiotracer within the tumor volume over the course of the 2 hour emission image. For final comparison, individual time-activity curves were normalized based on the injected radiotracer dose for each specific animal. Radiotracer uptake was compared across tumors using the final 10 minutes of each time-activity curve (1 hour 50 minutes-2 h post-radiotracer injection). Using this methodology, radiotracer uptake in hPD-L1(+) L2987 xenografts was 3.05× that seen hPD-L1(−) HT-29 xenografts in animals receiving only the ⁶⁴Cu-A02 radiotracer. In animals co-injected with the ⁶⁴Cu-A02 radiotracer and 3 mg/kg unlabeled A02 Adnectin uptake in the hPD-L1(+) L2987 xenografts was only 1.04× that seen in hPD-L1(−) HT-29 xenografts (FIGS. 4A and 4B).

Similar experiments using ¹⁸F as the radionuclide were conducted in mice, and similar results were obtained, reaching a maximum radiotracer uptake ratio of 3.53:1 in hPD-L1(+) L2987 xenografts vs. hPD-L1(−) HT-29 xenografts using the ¹⁸F-A02 Adnectin radiotracer. Briefly, nude mice were subcutaneously implanted bilaterally with HT-29 and L2987 cells. Once tumors reached approximately 200-300 mm³, animals were selected for imaging. Mice were anesthetized with 2% isoflurane in oxygen and placed onto the imaging bed of a Focus 120 PET imaging system (Siemens Preclinical Solutions). Approximately 150 μCi ¹⁸F-A02 was then injected via a tail vein and animals were imaged continuously for 120 minutes. A 10-minute transmission image was then collected using a ⁵⁷Co point source for use as attenuation correction. Images were reconstructed using a 3D maximum a posteriori algorithm with attenuation correction using AsiPro software (Siemens Preclinical Solutions). The results demonstrated clear differential uptake in hPD-L1 (=) L2987 xenografts compared to hPD-L1 (−) HT29 xenografts in mice receiving only the radiotracer.

For some studies, animals were sacrificed via cervical dislocation immediately following imaging. Necropsy was then performed on the animals, and individual tissues were collected (blood, heart, lung, liver, spleen, kidney, muscle, stomach, bone, L2987 tumor, and HT-29 tumor) into pre-weighed tubes. All tissues were then weighed again to determine the weight of each tissue. The radioactivity in each tissue was then directly measured ex vivo using a Perkin-Elmer Wizard3 gamma counter. For all tissues, measured values in counts per minute (CPM) were normalized to the injected radioactive dose for the individual animals and corrected for radioactive decay. These results were then plotted to show the biodistribution of the radiotracer. An example of this analysis for the ¹⁸F-A02 Adnectin radiotracer is shown in FIG. 5. These results demonstrate clear differential uptake of the radiotracer in hPD-L1(+) L2987 xenografts compared to hPD-L1(−) HT-29 xenografts. Furthermore, the only tissue with higher PD-L1 uptake was the kidney, which is expected as clearance of the ¹⁸F-A02 Adnectin is expected to be via kidney filtration based on the molecular weight of the molecule.

Taken together, these results provide direct visualization of differentiation of hPD-L1(+) versus hPD-L1(−) xenograft tumors in vivo. Specificity was further demonstrated by co-injection of 3 mg/kg unlabeled anti-PD-L1 A02 Adnectin, resulting in a reduction of radiotracer uptake in hPD-L1(+) tumors to the level of hPD-L1(−) xenografts. This further validates the use of anti-PD-L1 Adnectins for visualization of PD-L1 tissue expression using PET imaging.

The anti-PD-L1 Adnecin-based imaging agents also showed similar results when performed in cynomolgus monkeys. In these studies, the ¹⁸F-E01 anti-PD-L1 Adnectin, produced as described in the above Examples, was tested for its ability to produce high-contrast images in cynomolgus monkeys. The anti-PD-L1 Adnectins described here maintain high affinity for cynomolgus PD-L1 (but have low affinity for rodent PD-L1). Furthermore, as cynomolgus monkeys do not contain PD-L1(+) tumors as in mouse models, imaging performance was assessed primarily on the background levels measured in the images in the context of endogenous PD-L1 expression (with low background enabling the potential for high-sensitivity detection of PD-L1(+) tissues). In these studies, background levels in the resulting PET images were very low, with notable radiotracer accumulation noted mainly in the kidneys, spleen, and bladder.

Cynomolgus male monkeys with a previously installed vascular access port (VAP) were anesthetized with 0.02 mg/kg atropine, 5 mg/kg Telazol and 0.01 mg/kg buprenorphine I.M. (all drawn into a single syringe). An i.v. catheter is then placed in the cephalic vessel for fluid administration during the imaging procedure to maintain hydration. Animals were intubated with an endotracheal tube—usually 3.0 mm and transferred to the imaging bed of a microPET® F220™ PET instrument (Siemens Preclinical Solutions, Knoxville, Tenn.). Anesthesia was maintained with isoflurane and oxygen and I.V. fluids (LRS) were administered at a rate of 6 ml/kg/hr during the imaging procedure. As the axial field of view of the microPET® F220™ instrument is only 7.6 cm, images over 5 distinct bed positions were acquired to create a composite image of the animals from just above the heart through approximately the pelvis.

For each field of view, a 10 minute transmission image was first acquired using a ⁵⁷Co point source for the purpose of attenuation correction of the final PET images. Once transmission images were acquired for all bed positions, approximately 1.5 mCi (approximately 0.015 mg/kg) of the ¹⁸F-E01 Adnectin radiotracer was administered via the installed VAP. 5 minute duration emission scans were then sequentially acquired for each bed position, beginning at position 1 centered approximately at the heart and moving toward the pelvis of the animal. Once images were acquired at each position (1 through 5), the imaging bed was moved back to bed position 1 and the process was repeated. Using this procedure, a total of 5 distinct images were acquired for each bed position over the duration of the imaging study.

Individual images were reconstructed using a filtered back projection (FBP) algorithm with attenuation correction using the collected transmission images and corrected for radioisotope decay. Final composite images were then produced by aligning images from all 5 bed positions obtained from a single pass (i.e. a single composite image was produced from each set of sequential images from bed positions 1 through 5) covering the duration of the imaging study. Final images were visually inspected to note areas of visible radiotracer uptake (i.e. spleen, kidney, bladder) and background tissue (muscle) (FIG. 6). Background accumulation of ¹⁸F-E01 Adnectin was very low, with little signal visible in background tissues such as muscle. Additionally, uptake was verified in the spleen, which is believed to be PD-L1(+) based on mRNA expression. Thus, studies in cynomolgus monkeys demonstrate the potential for high-sensitivity PD-L1 imaging in the context of endogenous PD-L1.

In aggregate, PET studies in rodent and cynomolgus monkey show that ⁶⁴Cu and ¹⁸F labeled anti-human PD-L1 Adnectins provide strong and specific probes for in vivo labeling of PD-L1 positive tissues with the potential for high-sensitivity detection of tissues with low level PD-L1 expression.

In vivo imaging experiments were also conducted with an anti-PD-L1 antibody, and the areas that this imaging agent detected were the same areas that were detected with the PD-L1 imaging agent, therefore confirming that anti-PD-L1 Adnectin imaging agents successfully detect PD-L1 positive cells in vivo.

Example 16: In Vitro Autoradiography of Human and Xenograft Tissue with [¹⁸F]-E01 Anti-PD-L1 Adnectin

Human lung tumor tissues were embedded in OCT and chilled in 2-methylbutane for 2-5 minutes until frozen. Samples were stored in −80° C. degree freezer until use. Human xenograft tissues were also included in the assay. Mice bearing bilateral xenografts were produced by introducing 4×10⁶ hPD-L1(+) L2987 cells and 1.5×10⁶ hPD-L1(−) HT-29 t cells subcutaneously into opposite flanks of nu/nu mice. Once resulting xenograft tumors reached appropriate size (approx. 200-300 mm³), mice were anesthetized with 2% isoflurane and sacrificed via cervical dislocation. Fresh tumor tissues were excised, immersed into OCT and chilled in 2-methylbutane for 2-5 minutes until frozen. The tissues were then wrapped in foil/ZIPLOC® bag and stored at −80° C. until use. For all tissues (human lung tumor and xenografts) sections of 5 μm thickness (collected as 2 sections/slide) were cut using a cryostat, thaw-mounted on glass microscope slides, and allowed to air dry for approximately 30 minutes.

Blocking studies with cold (unlabeled) A02 Adnectin at 0.025 nM, 0.25 nM, 2.5 nM and 25 nM respectively and 25 nM non-PD-L1 binding Adnectin were conducted using the following conditions. The individual slides, 1 slide per concentration, were placed in plastic slide cassettes and pre-incubated in Dako serum-free protein block solution for 30 minutes. Slides were then transferred to glass slide incubation chambers for further incubation. Separately, a stock solution of 0.25 nM ¹⁸F-A02 Adnectin was produced by diluting 10.6 μl of the original stock radioligand solution (7064 nM at the time of experiment) with 300 ml of PBS+0.5% BSA. From this stock solution, 40 ml was added to each incubation chamber. One of these chambers contained only the radioligand buffer solution, which is referred to as the total binding section. Other incubation chambers received 40 ml of this stock solution along with the relevant concentration of blocking compound (unlabeled A02 Adnectin at 0.025 nM, 0.25 nM, 2.5 nM, or 25 nM or unlabeled non-PD-L1 binding Adnectin at 25 nM). Slides were incubated in the individual buffer solutions for 1 hour at room temperature to reach maximum binding. After incubation, slides from each treatment group were removed from the incubation solutions and placed in an ice-cold wash buffer (PBS+0.5% BSA) for 3 minutes and rinsed 4 separate times. Slides were then dried under a stream of cold air for approximately 30 minutes. The air-dried slides were exposed by placing the slides onto an imaging plate (BAS-SR 3545S) overnight at room temperature. The imaging plate was scanned using the bioimaging analyzer (Fujifilm Fluorescent Image Analyzer, FLA-9000). The pixel size of the autoradiogram images was 100 μm. Image analysis was performed using the Multi-Gauge software. The regions of interest (ROIs) were drawn to surround the entire tumor tissue in all study groups. Autogradiography signal from tissue-associated radioactivity was quantified from these ROIs.

The apparent displacement of the ¹⁸F-A02 Adnectin radioligand when compared to the total binding sections was determined for 4 different concentrations (0.025 nM, 0.25 nM, 2.5 nM and 25 nM) of unlabeled A02 Adnectin in both human lung tumor sections as well as human xenograft sections. A dose dependent displacement of ¹⁸F-A02 was seen in all tissue sections with the addition of unlabeled A02 Adnectin, while 25 nM non-PD-L1 binding Adnectin showed minimal blockade in all tissues compared to total binding (FIG. 7).

Serial 5 μm tissue sections from each tissue were subjected to an anti-human-PD-L1 immunohistochemical procedure to verify the level of PD-L1 antigen expression in the samples (FIG. 8).

Taken together, these results provide direct visualization of PD-L1 in both human lung tumor samples as well as human xenograft tissues. The level of radioligand binding in the individual tissues corresponds with the intensity of PD-L1 staining of frozen sections by IHC. In addition, the dose dependent blockade of the receptor with unlabeled anti-PD-L1 A02 Adnectin (and lack of blockade with unlabeled non-PD-L1 binding Adnectin), further validates the use of ¹⁸F-A02 for visualization of PD-L1 tissue expression using PET imaging.

Example 17: Automated Preparation of [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine According to the General Procedure for Radiosynthesis Using Commercial GE TRACERlab FX2 N Synthesis Unit

Procedure:

The automated synthesis of [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine was carried out using a non-cassette type GE TRACERlab FX2 N Synthesis module. The setup of the synthesis unit is summarized in Table 4. The aqueous [¹⁸F]-Fluoride solution (2.0 ml, 29.6 GBq/800 mCi) was delivered to a Sep-Pak light QMA [The Sep-Pak light QMA cartridge was pre-conditioned sequentially with 5 ml of 0.5 M potassium bicarbonate, 5 ml of deionized water, and 5 ml of acetonitrile before use.] Upon completion of this transfer, the aqueous [¹⁸F] fluoride was released from the QMA Sep-Pak by the addition of the elution mixture (from “V1”) into the reactor. The solvent was evaporated under a gentle stream of nitrogen and vacuum. The solution of precursor (from “V3”) was added to the dried cryptand residue and this reaction mixture was heated 120° C. for 10 minutes. Then 4 ml of distilled water (from “V4”) was added to the crude reaction mixture in the reactor and the mixture was transferred to the 5 ml sample injection loop of the semi-preparative HPLC via a liquid sensor which controls the end of the loading. The mixture was loaded onto the semi-preparative HPLC column (Luna C18(2). 250×10 mm, Phenomenex). A mixture of 35% acetonitrile in an aqueous 0.1% trifluoroacetic acid solution was flushed through the column at a rate of 4.6 ml per minute. The product was collected from this HPLC column into the dilution flask which contained 15 ml distilled water and its entire contents were transferred to a tC18 1 gram, solid phase extraction cartridge. 352 mCi (13 GBq) of [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine was released from this cartridge (from “V14”) with 3 ml of ethanol and may be used to generate ¹⁸F labeled biologic products by taking advantage of “click” azide-alkyne reaction with the appropriate biologic containing an alkynes.

TABLE 4 Vial 1 (V1) 16 mg K.2.2.2, 3 mg Potassium carbonate, dissolved in 0.1 ml of distilled water and 1.4 ml of acetonitrile Vial 3 (V3) 2 mg 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)eth- oxy)-2-nitropyridine in 0.5 ml DMSO Vial 4 (V4) 4 ml of distilled water Vial 14 (V14) 3 ml of 100% ethanol Dilution Flask 15 ml of distilled water Cartridge 1 (C1) tC18 6 cc 1 g sep pack HPLC Column Luna C18(2), 250 × 10 mm, 5 μm, Phenomenex HPLC Solvent 35% acetonitrile in an aqueous 0.1% trifluoroacetitic acid solution HPLC flow 4.6 ml/min

Example 18 Automated Preparation of [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine According to the General Procedure for Radiosynthesis on IBA Synthera Synthesis Unit

Procedure:

The automated synthesis of [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine was carried out using a cassette type IBA Synthera Synthesis module and an appropriately assembled integrator fluidic processor kit. The integrator fluidic processor (IFP) kit was loaded with appropriate precursors for this synthesis and is summarized in Table 5. The purification was performed on an Varian HPLC unit. The filling of the injection loop of the HPLC was controlled by a steady stream of nitrogen on the HPLC unit. The setup of both automates are summarized in Table 5. The aqueous [¹⁸F]-Fluoride solution (2.0 ml, 29.6 GBq/800 mCi) was delivered to a Sep-Pak light QMA [The Sep-Pak light QMA cartridge was pre-conditioned sequentially with 5 ml of 0.5 M potassium bicarbonate, 5 ml of deionized water, and 5 ml of acetonitrile before use.] Upon completion of this transfer, the aqueous [18F] fluoride was released from the QMA Sep-Pak by the addition of the elution mixture (from “V1”) into the reactor. The solvent was evaporated under a gentle stream of nitrogen and vacuum. The solution of precursor (from “V2”) was added to the dried cryptand residue and this reaction mixture was heated 120° C. for 10 minutes. Then 3 ml of distilled water (from “V4”) was added to the crude reaction mixture in the reactor and the mixture is transferred to the 5 ml sample injection loop of the semi-preparative HPLC via a liquid sensor which controls the end of the loading. The mixture was loaded onto the semi-preparative HPLC column (Luna C18(2). 250×10 mm, Phenomenex). A mixture of 35% acetonitrile in an aqueous 0.1% trifluoroacetic acid solution was flushed through the column at a rate of 4.6 ml per minute. The product was collected from this HPLC column into the dilution flask which contained 15 ml distilled water and its entire contents were transferred to a tC18 1 gram, solid phase extraction cartridge. 325 mCi (12 GBq) of [¹⁸F]-3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethoxy)-2-fluoropyridine was released from this cartridge with 3 ml of ethanol and may be used to generate ¹⁸F labeled biologic products by taking advantage of “click” azide-alkyne reaction with the appropriate biologic containing an alkynes.

TABLE 5 Vial 1 (V1) 22 mg K.2.2.2, 4 mg Potassium carbonate, dissolved in 0.3 ml of distilled water and 0.3 ml of acetonitrile Vial 2 (V2) 2 mg 3-(2-(2-(2-(2-azidoethoxy)ethoxy)ethoxy)eth- oxy)-2-nitropyridine in 0.5 ml DMSO Vial 4 (V4) 3 ml of distilled water Dilution Flask 15 ml of distilled water Cartridge 1 (C1) tC18 6 cc 1 g sep pack HPLC Column Luna C18(2), 250 × 10 mm, 5 μm, Phenomenex HPLC Solvent 35% acetonitrile in an aqueous 0.1% trifluoroacetitic acid solution HPLC flow 4.6 ml/min

Example 19: Synthesis of ⁶⁸Ga-Based Anti-PD-L1 Adnectin Probes

Synthesis of ⁶⁸Ga-E01-NODAGA

[⁶⁸Ga]-Gallium chloride in 0.1N hydrochloric acid solution was neutralized with 32 mg of sodium acetate (NaOAc) for 4 minutes at ambient temperature, the resultant solution was stirred to ensure the entire volume was properly mixed. This solution was then added to E01-NODAGA (15 μL of 1.3 mg/mL) solution and the crude reaction was gently pipetted to allow mixing followed by resting at ambient temperature for 15 minutes. The contents of crude reaction mixture were transferred to a PD-10 desalting column that was pre-activated with 20 mL of 1× phosphate buffered saline (PBS, pH 7.4) buffer prior to loading of sample. An additional 1.5 mL of 1×PBS was added to the column, followed by an additional 0.8 ml 1×PBS solution and these fractions were discarded. [⁶⁸Ga]-E01-NODAGA was then collected after a 1.4 mL elution of the PD-10 column to give 5.78 mCi (214 MBq) as the desired product. Quality control was measured using a reverse phase HPLC system using an Agilent PLRP-S HPLC column Size: 250×4.60 mm, 8 μm, 280 nm and a mobile phase of 0.1% Formic Acid in distilled water and acetonitrile. A gradient method was used where the percentage of acetonitrile was increased linearly from 10% to 45% over a 30 minute time frame. [⁶⁸Ga]-E01-NODAGA co-eluted with reference standard at the 22 minute mark of the HPLC chromatogram. Radiochemical purity was measured to be 98% using this method. [⁶⁸Ga]-E01-NODAGA also co-eluted with reference material at the 20 minute mark using a size exclusion chromatography, (SEC) Column: GE Superdex 200 GL Size: 10×300 mm, 280 nm.

Example 20: Pharmacokinetics of [¹⁹F]-E01 Anti-PD-L1 Adnectin

The following experiment was conducted to compare the pharmacokinetics of ¹⁹F labelled-E01 anti-PD-L1 adnectin and E01-4PEG-DBCO (unlabeled anti-PD-L1-adnectin-DBCO precursor) in cynomolgus monkeys (n=3). This was a cross-over design study with a 2-week washout between doses. Serum samples were collected and analyzed by either a LBA using specific adnectin-binding reagents that do not differentiate E01-4PEG-DBCO from [¹⁹F]-E01, or LC/MS assays that differentiate between E01-4PEG-DBCO and [¹⁹F]-E01.

A summary of the PK parameters is shown in Table 6.

TABLE 6 [¹⁹F]-E01 E01-4PEG-DBCO AUC(INF) (μg*h/mL) 4.72 ± 0.79 2.92 ± 0.40 CLTs (mL/min/kg) 4.54 ± 0.81 5.78 ± 0.76 Vss (L/kg) 0.29 ± 0.05 0.40 ± 0.04 T-HALF (h) 1.69 ± 0.13 1.65 ± 0.13 MRT (h) 1.05 ± 0.06 1.14 ± 0.05

Following an i.v. dose to cynomolgus monkeys, the CLTs of [¹⁹F]-E01 was low in both studies. The T-HALF was also short, at about 1.7 hours. The PK of E01-4PEG-DBCO was similar to that of [¹⁹F]-E01. The PK parameters were also similar by LC/MS.

TABLE 3  SEQUENCE LISTING SEQ ID DESCRIPTION SEQUENCE 1 Full length wild-type VSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITYGETGGNS human ¹⁰Fn3 domain PVQEFTVPGSKSTATISGLKPGVDYTITVYAVTGRGDSPASSK PISINYRT 2 Core wild-type human EVVAATPTSLLISWDAPAVTVRYYRITYGETGGNSPVQEFTVP  ¹⁰Fn3 domain GSKSTATISGLKPGVDYTITVYAVTGRGDSPASSKPISINYRT 3 Core ¹⁰Fn3-based scaffold EVVAA(Z)_(a)LLISW(Z)_(x)YRITY(Z)_(b)FTV(Z)_(y)ATISGL(Z)_(c)Y with variable AB, BC, CD, TITVYA(Z)_(z)ISINYRT DE, EF, and FG loops 4 Core ¹⁰Fn3-based scaffold EVVAATPTSLLISW(Z_(x)YRITYGETGGNSPVQEFTV(Z)_(y)ATISG with variable BC, DE, and LKPGVDYTITVYA(Z)_(z)ISINYRT FG loops 5 ATI-968 core (aka EVVAATPTSLLISWIAPFYNVIYYRITYGETGGNSPVQEFTVPGTG ADX_1760_C01) YTATISGLKPGVDYTITVYAVTDGASIASYAFPISINYRT 6 ATI-968 BC loop IAPFYNVIY 7 ATI-968 DE loop PGTGYT 8 ATI-968 FG loop VTDGASIASYAFP  9 ATI-968 w/ N leader GVSDVPRDLEVVAATPTSLLISWIAPFYNVIYYRITYGETGGNSPV QEFTVPGTGYTATISGLKPGVDYTITVYAVTDGASIASYAFPISIN YRT 10 ATI-968 w/ N leader + his GVSDVPRDLEVVAATPTSLLISWIAPFYNVIYYRITYGETGGNSPV tag QEFTVPGTGYTATISGLKPGVDYTITVYAVTDGASIASYAFPISIN YRTHHHHHH 11 ATI-968 w/ N leader and C GVSDVPRDLEVVAATPTSLLISWIAPFYNVIYYRITYGETGGNSPV tail QEFTVPGTGYTATISGLKPGVDYTITVYAVTDGASIASYAFPISIN YRTEIDKPSQ 12 ATI-968 w/ N leader and C GVSDVPRDLEVVAATPTSLLISWIAPFYNVIYYRITYGETGGNSPV tail + his tag QEFTVPGTGYTATISGLKPGVDYTITVYAVTDGASIASYAFPISIN YRTEIDKPSQHHHHHH 13 ATI-968 w/ N leader and GVSDVPRDLEVVAATPTSLLISWIAPFYNVIYYRITYGETGGNSPV modified C-terminus QEFTVPGTGYTATISGLKPGVDYTITVYAVTDGASIASYAFPISIN including PC YRTPC 14 ATI-968 w/ N leader and GVSDVPRDLEVVAATPTSLLISWIAPFYNVIYYRITYGETGGNSPV modified C-terminus QEFTVPGTGYTATISGLKPGVDYTITVYAVTDGASIASYAFPISIN including PC + his tag YRTPCHHHHHH 15 ATI-968-full length MGVSDVPRDLEVVAATPTSLLISWIAPFYNVIYYRITYGETGGNSP  VQEFTVPGTGYTATISGLKPGVDYTITVYAVTDGASIASYAFPISI NYRTEIDKPSQHHHHHH 16 ATI-968-core (nucleotide GAAGTGGTTGCTGCCACCCCCACCAGCCTGCTGATCAGCTGGATCG sequence) CTCCGTTCTACAATGTCATCTATTACCGCATCACTTACGGCGAAAC AGGAGGCAATAGCCCTGTCCAGGAGTTCACTGTGCCTGGTACTGGT TATACAGCTACAATCAGCGGCCTTAAACCTGGCGTTGATTATACCA TCACTGTGTATGCTGTCACTGATGGAGCATCCATTGCTTCATACGC GTTTCCAATTTCCATTAATTACCGCACA 17 ATI-968 w/ N leader ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA (nucleotide sequence with CCCCCACCAGCCTGCTGATCAGCTGGATCGCTCCGTTCTACAATGT N-terminal methionine) CATCTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT GTCCAGGAGTTCACTGTGCCTGGTACTGGTTATACAGCTACAATCA GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CACTGATGGAGCATCCATTGCTTCATACGCGTTTCCAATTTCCATT AATTACCGCACA 18 ATI-968 w/ N leader and ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA modified C-terminus CCCCCACCAGCCTGCTGATCAGCTGGATCGCTCCGTTCTACAATGT including PC (nucleotide CATCTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT sequence with N-terminal GTCCAGGAGTTCACTGTGCCTGGTACTGGTTATACAGCTACAATCA methionine) GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CACTGATGGAGCATCCATTGCTTCATACGCGTTTCCAATTTCCATT AATTACCGCACACCGTGC 19 ATI-968 w/ N leader and C ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA tail + his tag (nucleotide CCCCCACCAGCCTGCTGATCAGCTGGATCGCTCCGTTCTACAATGT sequence with N-terminal CATCTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT methionine) GTCCAGGAGTTCACTGTGCCTGGTACTGGTTATACAGCTACAATCA GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CACTGATGGAGCATCCATTGCTTCATACGCGTTTCCAATTTCCATT AATTACCGCACAGAAATTGACAAACCATCCCAGCACCATCACCACC ACCACTGA 20 ATI-964 core (parent of EVVAATPTSLLISWSYDGSIERYYRITYGETGGNSPVQEFTVPPDQ ADX_5322_A02) KTATISGLKPGVDYTITVYAVRLEEAHYYRESPISINYRT 21 ATI-964 BC loop SYDGSIERY 22 ATI-964 DE loop PPDQKT 23 ATI-964 FG loop VRLEEAHYYRESP  24 ATI-964 w/ N leader GVSDVPRDLEVVAATPTSLLISWSYDGSIERYYRITYGETGGNSPV QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYYRESPISIN YRT 25 ATI-964 w/ N leader + his  GVSDVPRDLEVVAATPTSLLISWSYDGSIERYYRITYGETGGNSPV tag QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYYRESPISIN YRTHHHHHH 26 ATI-964 w/ N leader and C  GVSDVPRDLEVVAATPTSLLISWSYDGSIERYYRITYGETGGNSPV tail QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYYRESPISIN YRTEIDKPSQ 27 ATI-964 w/ N leader and C  GVSDVPRDLEVVAATPTSLLISWSYDGSIERYYRITYGETGGNSPV tail + his tag QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYYRESPISIN YRTEIDKPSQHHHHHH 28 ATI-964 w/ N leader and GVSDVPRDLEVVAATPTSLLISWSYDGSIERYYRITYGETGGNSPV modified C-terminus QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYYRESPISIN including PC YRTPC 29 ATI-964 w/ N leader and GVSDVPRDLEVVAATPTSLLISWSYDGSIERYYRITYGETGGNSPV modified C-terminus QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYYRESPISIN including PC + his tag YRTPCHHHHHH 30 ATI-964-full length MGVSDVPRDLEVVAATPTSLLISWSYDGSIERYYRITYGETGGNSP VQEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYYRESPISI NYRTEIDKPSQHHHHHH 31 ATI-964-core (nucleotide  GAAGTGGTTGCTGCCACCCCCACCAGCCTGCTGATCAGCTGGTCTT sequence) ACGACGGTTCGATTGAACGTTATTACCGCATCACTTACGGCGAAAC AGGAGGCAATAGCCCTGTCCAGGAGTTCACTGTGCCTCCGGATCAG AAGACAGCTACCATCAGCGGCCTTAAACCTGGCGTTGATTATACCA TCACTGTGTATGCTGTCAGGCTGGAAGAAGCTCATTACTATCGAGA GTCTCCAATTTCCATTAATTACCGCACA 32 ATI-964 w/ N leader ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA (nucleotide sequence with CCCCCACCAGCCTGCTGATCAGCTGGTCTTACGACGGTTCGATTGA N-terminal methionine) ACGTTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT GTCCAGGAGTTCACTGTGCCTCCGGATCAGAAGACAGCTACCATCA GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CAGGCTGGAAGAAGCTCATTACTATCGAGAGTCTCCAATTTCCATT AATTACCGCACA 33 ATI-964 w/ N leader and ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA modified C-terminus CCCCCACCAGCCTGCTGATCAGCTGGTCTTACGACGGTTCGATTGA including PC (nucleotide ACGTTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT sequence with N-terminal GTCCAGGAGTTCACTGTGCCTCCGGATCAGAAGACAGCTACCATCA methionine) GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CAGGCTGGAAGAAGCTCATTACTATCGAGAGTCTCCAATTTCCATT AATTACCGCACACCGTGC 34 ATI-964 w/ N leader and C  ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA tail + his tag  CCCCCACCAGCCTGCTGATCAGCTGGTCTTACGACGGTTCGATTGA (nucleotide sequence with  ACGTTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT N-terminal methionine) GTCCAGGAGTTCACTGTGCCTCCGGATCAGAAGACAGCTACCATCA GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CAGGCTGGAAGAAGCTCATTACTATCGAGAGTCTCCAATTTCCATT AATTACCGCACAGAAATTGACAAACCATCCCAGCACCATCACCACC ACCACTGA 35 ATI-965 core EVVAATPTSLLISWTAYDSVDKYYRITYGETGGNSPVQEFTVGPRH HTATISGLKPGVDYTITVYAVYHTEPGYHAHMPISINYRT 36 ATI-965 BC loop TAYDSVDKY 37 ATI-965 DE loop GPRHHT 38 ATI-965 FG loop VYHTEPGYHAHMP  39 ATI-965 w/ N leader GVSDVPRDLEVVAATPTSLLISWTAYDSVDKYYRITYGETGGNSPV QEFTVGPRHHTATISGLKPGVDYTITVYAVYHTEPGYHAHMPISIN YRT 40 ATI-965 w/ N leader + his GVSDVPRDLEVVAATPTSLLISWTAYDSVDKYYRITYGETGGNSPV tag QEFTVGPRHHTATISGLKPGVDYTITVYAVYHTEPGYHAHMPISIN YRTHHHHHH 41 ATI-965 w/ N leader and C GVSDVPRDLEVVAATPTSLLISWTAYDSVDKYYRITYGETGGNSPV tail QEFTVGPRHHTATISGLKPGVDYTITVYAVYHTEPGYHAHMPISIN YRTEIDKPSQ 42 ATI-965 w/ N leader and C GVSDVPRDLEVVAATPTSLLISWTAYDSVDKYYRITYGETGGNSPV tail + his tag QEFTVGPRHHTATISGLKPGVDYTITVYAVYHTEPGYHAHMPISIN YRTEIDKPSQHHHHHH 43 ATI-965 w/ N leader and GVSDVPRDLEVVAATPTSLLISWTAYDSVDKYYRITYGETGGNSPV modified C-terminus QEFTVGPRHHTATISGLKPGVDYTITVYAVYHTEPGYHAHMPISIN including PC YRTPC 44 ATI-965 w/ N leader and GVSDVPRDLEVVAATPTSLLISWTAYDSVDKYYRITYGETGGNSPV modified C-terminus QEFTVGPRHHTATISGLKPGVDYTITVYAVYHTEPGYHAHMPISIN including PC + his tag YRTPCHHHHHH 45 ATI-965-full length MGVSDVPRDLEVVAATPTSLLISWTAYDSVDKYYRITYGE TGGNSPVQEFTVGPRHHTATISGLKPGVDYTITVYAVYHTEPGYHA HMPISINYRTEIDKPSQHHHHHH 46 ATI-965-core (nucleotide  GAAGTGGTTGCTGCCACCCCCACCAGCCTGCTGATCAGCTGGACTG sequence) CATACGACTCTGTTGACAAATATTACCGCATCACTTACGGCGAAAC AGGAGGCAATAGCCCTGTCCAGGAGTTCACTGTGGGCCCTAGACAT CACACAGCTACCATCAGCGGCCTTAAACCTGGCGTTGATTATACCA TCACTGTGTATGCTGTCTATCACACTGAACCGGGCTATCATGCTCA TATGCCAATTTCCATTAATTACCGCACA 47 ATI-965 w/ N leader ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA (nucleotide sequence with CCCCCACCAGCCTGCTGATCAGCTGGACTGCATACGACTCTGTTGA N-terminal methionine) CAAATATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT GTCCAGGAGTTCACTGTGGGCCCTAGACATCACACAGCTACCATCA GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CTATCACACTGAACCGGGCTATCATGCTCATATGCCAATTTCCATT AATTACCGCACA 48 ATI-965 w/ N leader and ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA modified C-terminus CCCCCACCAGCCTGCTGATCAGCTGGACTGCATACGACTCTGTTGA including PC (nucleotide CAAATATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT sequence with N-terminal GTCCAGGAGTTCACTGTGGGCCCTAGACATCACACAGCTACCATCA methionine) GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CTATCACACTGAACCGGGCTATCATGCTCATATGCCAATTTCCATT AATTACCGCACACCGTGC 49 ATI-965 w/ N leader and C  ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA tail + his tag   CCCCCACCAGCCTGCTGATCAGCTGGACTGCATACGACTCTGTTGA (nucleotide sequence with CAAATATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT N-terminal methionine) GTCCAGGAGTTCACTGTGGGCCCTAGACATCACACAGCTACCATCA GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CTATCACACTGAACCGGGCTATCATGCTCATATGCCAATTTCCATT AATTACCGCACAGAAATTGACAAACCATCCCAGCACCATCACCACC ACCACTGA 50 ATI-966 core EVVAATPTSLLISWHRFSSIMAYYRITYGETGGNSPVQEFTVAGSV NTATISGLKPGVDYTITVYAVTIHNVSFPISINYRT 51 ATI-966 BC loop HRFSSIMAY 52 ATI-966 DE loop AGSVNT 53 ATI-966 FG loop VTIHNVSFP  54 ATI-966 w/ N leader GVSDVPRDLEVVAATPTSLLISWHRFSSIMAYYRITYGETGGNSPV QEFTVAGSVNTATISGLKPGVDYTITVYAVTIHNVSFPISINYRT 55 ATI-966 w/ N leader + his  GVSDVPRDLEVVAATPTSLLISWHRFSSIMAYYRITYGETGGNSPV tag QEFTVAGSVNTATISGLKPGVDYTITVYAVTIHNVSFPISINYRTH HHHHH 56 ATI-966 w/ N leader and C  GVSDVPRDLEVVAATPTSLLISWHRFSSIMAYYRITYGETGGNSPV tail QEFTVAGSVNTATISGLKPGVDYTITVYAVTIHNVSFPISINYRTE IDKPSQ 57 ATI-966 w/ N leader and C  GVSDVPRDLEVVAATPTSLLISWHRFSSIMAYYRITYGETGGNSPV tail + his tag QEFTVAGSVNTATISGLKPGVDYTITVYAVTIHNVSFPISINYRTE IDKPSQHHHHHH 58 ATI-966 w/ N leader and GVSDVPRDLEVVAATPTSLLISWHRFSSIMAYYRITYGETGGNSPV modified C-terminus QEFTVAGSVNTATISGLKPGVDYTITVYAVTIHNVSFPISINYRTP including PC C 59 ATI-966 w/ N leader and GVSDVPRDLEVVAATPTSLLISWHRFSSIMAYYRITYGETGGNSPV modified C-terminus QEFTVAGSVNTATISGLKPGVDYTITVYAVTIHNVSFPISINYRTP including PC + his tag CHHHHHH 60 ATI-966-full length MGVSDVPRDLEVVAATPTSLLISWHRFSSIMAYYRITYGETGGNSP VQEFTVAGSVNTATISGLKPGVDYTITVYAVTIHNVSFPISINYRT EIDKPSQHHHHHH 61 ATI-966-core (nucleotide  GAAGTGGTTGCTGCCACCCCCACCAGCCTGCTGATCAGCTGGCATA sequence) GGTTCTCTTCTATCATGGCGTATTACCGCATCACTTACGGCGAAAC AGGAGGCAATAGCCCTGTCCAGGAGTTCACTGTGGCTGGCTCTGTT AACACAGCTACCATCAGCGGCCTTAAACCTGGCGTTGATTATACCA TCACTGTGTATGCTGTCACGATCCATAACGTTTCTTTCCCAATTTC CATTAATTACCGCACA 62 ATI-966w/ N leader ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA (nucleotide sequence with CCCCCACCAGCCTGCTGATCAGCTGGCATAGGTTCTCTTCTATCAT N-terminal methionine) GGCGTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT GTCCAGGAGTTCACTGTGGCTGGCTCTGTTAACACAGCTACCATCA GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CACGATCCATAACGTTTCTTTCCCAATTTCCATTAATTACCGCACA 63 ATI-966 w/ N leader and ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA modified C-terminus CCCCCACCAGCCTGCTGATCAGCTGGCATAGGTTCTCTTCTATCAT including PC (nucleotide GGCGTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT sequence with N-terminal GTCCAGGAGTTCACTGTGGCTGGCTCTGTTAACACAGCTACCATCA methionine) GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CACGATCCATAACGTTTCTTTCCCAATTTCCATTAATTACCGCACA CCGTGC 64 ATI-966 w/ N leader and C  ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA tail + his tag   CCCCCACCAGCCTGCTGATCAGCTGGCATAGGTTCTCTTCTATCAT (nucleotide sequence with GGCGTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT N-terminal methionine) GTCCAGGAGTTCACTGTGGCTGGCTCTGTTAACACAGCTACCATCA GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CACGATCCATAACGTTTCTTTCCCAATTTCCATTAATTACCGCACA GAAATTGACAAACCATCCCAGCACCATCACCACCACCACTGA 65 ATI-967 core (parent of EVVAATPTSLLISWQGQLSPSFYYRITYGETGGNSPVQEFTVPVAS ADX_5417_E01) GTATISGLKPGVDYTITVYAVTSHGIYFYAPISINYRT 66 ATI-967 BC loop QGQLSPSFY 67 ATI-967 DE loop PVASGT 68 ATI-967 FG loop VTSHGIYFYAP  69 ATI-967 w/ N leader GVSDVPRDLEVVAATPTSLLISWQGQLSPSFYYRITYGETGGNSPV QEFTVPVASGTATISGLKPGVDYTITVYAVTSHGIYFYAPISINYR T 70 ATI-967 w/ N leader + his  GVSDVPRDLEVVAATPTSLLISWQGQLSPSFYYRITYGETGGNSPV tag QEFTVPVASGTATISGLKPGVDYTITVYAVTSHGIYFYAPISINYR THHHHHH 71 ATI-967 w/ N leader and C  GVSDVPRDLEVVAATPTSLLISWQGQLSPSFYYRITYGETGGNSPV tail QEFTVPVASGTATISGLKPGVDYTITVYAVTSHGIYFYAPISINYR TEIDKPSQ 72 ATI-967 w/ N leader and C  GVSDVPRDLEVVAATPTSLLISWQGQLSPSFYYRITYGETGGNSPV tail + his tag QEFTVPVASGTATISGLKPGVDYTITVYAVTSHGIYFYAPISINYR TEIDKPSQHHHHHH 73 ATI-967 w/ N leader and GVSDVPRDLEVVAATPTSLLISWQGQLSPSFYYRITYGETGGNSPV modified C-terminus QEFTVPVASGTATISGLKPGVDYTITVYAVTSHGIYFYAPISINYR including PC TPC 74 ATI-967 w/ N leader and GVSDVPRDLEVVAATPTSLLISWQGQLSPSFYYRITYGETGGNSPV modified C-terminus QEFTVPVASGTATISGLKPGVDYTITVYAVTSHGIYFYAPISINYR including PC + his tag TPCHHHHHH 75 ATI-967-full length MGVSDVPRDLEVVAATPTSLLISWQGQLSPSFYYRITYGETGGNSP VQEFTVPVASGTATISGLKPGVDYTITVYAVTSHGIYFYAPISINY RTEIDKPSQHHHHHH 76 ATI-967-core (nucleotide  GAAGTGGTTGCTGCCACCCCCACCAGCCTGCTGATCAGCTGGCAGG sequence) GACAGCTGTCTCCGTCTTTCTATTACCGAATCACTTACGGCGAAAC AGGAGGCAATAGCCCTGTCCAGGAGTTCACTGTGCCTGTTGCTAGT GGGACAGCTACCATCAGCGGCCTTAAACCTGGCGTTGATTATACCA TCACTGTGTATGCTGTCACTTCTCATGGCATATACTTCTACGCTCC AATTTCCATTAATTACCGCACA 77 ATI-967 w/ N leader ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA (nucleotide sequence with CCCCCACCAGCCTGCTGATCAGCTGGCAGGGACAGCTGTCTCCGTC N-terminal methionine) TTTCTATTACCGAATCACTTACGGCGAAACAGGAGGCAATAGCCCT GTCCAGGAGTTCACTGTGCCTGTTGCTAGTGGGACAGCTACCATCA GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CACTTCTCATGGCATATACTTCTACGCTCCAATTTCCATTAATTAC CGCACA 78 ATI-967 w/ N leader and ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA modified C-terminus CCCCCACCAGCCTGCTGATCAGCTGGCAGGGACAGCTGTCTCCGTC including PC (nucleotide TTTCTATTACCGAATCACTTACGGCGAAACAGGAGGCAATAGCCCT sequence with N-terminal GTCCAGGAGTTCACTGTGCCTGTTGCTAGTGGGACAGCTACCATCA methionine) GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CACTTCTCATGGCATATACTTCTACGCTCCAATTTCCATTAATTAC CGCACACCGTGC 79 ATI-967 w/ N leader and C  ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA tail + his tag   CCCCCACCAGCCTGCTGATCAGCTGGCAGGGACAGCTGTCTCCGTC (nucleotide sequence with TTTCTATTACCGAATCACTTACGGCGAAACAGGAGGCAATAGCCCT N-terminal methionine) GTCCAGGAGTTCACTGTGCCTGTTGCTAGTGGGACAGCTACCATCA GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CACTTCTCATGGCATATACTTCTACGCTCCAATTTCCATTAATTAC CGCACAGAAATTGACAAACCATCCCAGCACCATCACCACCACCACT GAT 80 ADX_5322_A02 core EVVAATPTSLLISWSYDGPIDRYYRITYGETGGNSPVQEFTVPPDQ KTATISGLKPGVDYTITVYAVRLEEAHYNREFPISINYRT 81 ADX_5322_A02 BC loop SYDGPIDRY 82 ADX_5322_A02 DE loop PPDQKT 83 ADX_5322_A02 FG loop VRLEEAHYNREFP  84 ADX_5322_A02 w/ N GVSDVPRDLEVVAATPTSLLISWSYDGPIDRYYRITYGETGGNSPV leader QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYNREFPISIN YRT 85 ADX_5322_A02 w/ N GVSDVPRDLEVVAATPTSLLISWSYDGPIDRYYRITYGETGGNSPV leader + his ta g QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYNREFPISIN YRTHHHHHH 86 ADX_5322_A02 w/ N GVSDVPRDLEVVAATPTSLLISWSYDGPIDRYYRITYGETGGNSPV leader and C tail QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYNREFPISIN YRTEIDKPSQ 87 ADX_5322_A02 w/ N GVSDVPRDLEVVAATPTSLLISWSYDGPIDRYYRITYGETGGNSPV leader and C tail + his tag QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYNREFPISIN YRTEIDKPSQHHHHHH 88 ADX_5322_A02 w/ N GVSDVPRDLEVVAATPTSLLISWSYDGPIDRYYRITYGETGGNSPV leader and modified C- QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYNREFPISIN terminus including PC YRTPC 89 ADX_5322_A02 w/ N GVSDVPRDLEVVAATPTSLLISWSYDGPIDRYYRITYGETGGNSPV leader and modified C- QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYNREFPISIN terminus including PC + YRTPCHHHHHH his tag 90 ADX_5322_A02-Mal- GVSDVPRDLEVVAATPTSLLISWSYDGPIDRYYRITYGETGGNSPV DBCO-FFPF18 QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYNREFPISIN YRTPC-[Maleamide-DBCO-FFP(18F)] 91 ADX_5322_A02 full MGVSDVPRDLEVVAATPTSLLISWSYDGPIDRYYRITYGETGGNSP length VQEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYNREFPISI NYRTPCHHHHHH 92 ADX_5322_A02-core GAAGTGGTTGCTGCCACCCCCACCAGCCTGCTGATCAGCTGGTCTT (nucleotide sequence) ACGATGGCCCAATTGACCGGTATTACCGCATCACTTACGGCGAAAC AGGAGGCAATAGCCCTGTCCAGGAGTTCACTGTGCCTCCGGATCAG AAGACAGCTACCATCAGCGGCCTTAAACCTGGCGTTGATTATACCA TCACTGTGTATGCTGTCCGGCTGGAAGAAGCTCATTACAATCGAGA GTTTCCAATTTCCATTAATTACCGCACA 93 ADX_5322_A02 w/ N ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA leader (nucleotide CCCCCACCAGCCTGCTGATCAGCTGGTCTTACGATGGCCCAATTGA sequence with N-terminal  CCGGTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT methionine) GTCCAGGAGTTCACTGTGCCTCCGGATCAGAAGACAGCTACCATCA GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CCGGCTGGAAGAAGCTCATTACAATCGAGAGTTTCCAATTTCCATT AATTACCGCACA 94 ADX_5322_A02 w/ N ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA leader and modified C- CCCCCACCAGCCTGCTGATCAGCTGGTCTTACGATGGCCCAATTGA terminus including PC CCGGTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT (nucleotide sequence with GTCCAGGAGTTCACTGTGCCTCCGGATCAGAAGACAGCTACCATCA N-terminal methionine) GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CCGGCTGGAAGAAGCTCATTACAATCGAGAGTTTCCAATTTCCATT AATTACCGCACACCGTGC 95 ADX_5322_A02 w/ N ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA leader and C tail +  CCCCCACCAGCCTGCTGATCAGCTGGTCTTACGATGGCCCAATTGA his tag (nucleotide  CCGGTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT sequence with GTCCAGGAGTTCACTGTGCCTCCGGATCAGAAGACAGCTACCATCA N-terminal methionine) GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CCGGCTGGAAGAAGCTCATTACAATCGAGAGTTTCCAATTTCCATT AATTACCGCACACCGTGCCACCATCACCACCACCACTGA 96 ADX_5417_E01 core EVVAATPTSLLISWRAQLSPSFYYRITYGETGGNSPVQEFTVPNDV MTATISGLKPGVDYTITVYAVTTHGVYFYSPISINYRT 97 ADX_5417_E01 BC loop RAQLSPSFY 98 ADX_5417_E01 DE loop PNDVMT 99 ADX_5417_E01 FG loop VTTHGVYFYSP  100 ADX_5417_E01 w/ N GVSDVPRDLEVVAATPTSLLISWRAQLSPSFYYRITYGETGGNSPV leader QEFTVPNDVMTATISGLKPGVDYTITVYAVTTHGVYFYSPISINYR T 101 ADX_5417_E01 w/ N GVSDVPRDLEVVAATPTSLLISWRAQLSPSFYYRITYGETGGNSPV leader + his tag QEFTVPNDVMTATISGLKPGVDYTITVYAVTTHGVYFYSPISINYR THHHHHH 102 ADX_5417_E01 w/ N GVSDVPRDLEVVAATPTSLLISWRAQLSPSFYYRITYGETGGNSPV leader and C tail QEFTVPNDVMTATISGLKPGVDYTITVYAVTTHGVYFYSPISINYR TEIDKPSQ 103 ADX_5417_E01 w/ N GVSDVPRDLEVVAATPTSLLISWRAQLSPSFYYRITYGETGGNSPV leader and C tail +  QEFTVPNDVMTATISGLKPGVDYTITVYAVTTHGVYFYSPISINYR his tag TEIDKPSQHHHHHH 104 ADX_5417_E01 w/ N GVSDVPRDLEVVAATPTSLLISWRAQLSPSFYYRITYGETGGNSPV leader and modified C- QEFTVPNDVMTATISGLKPGVDYTITVYAVTTHGVYFYSPISINYR terminus including PC TPC 105 ADX_5417_E01 w/ N GVSDVPRDLEVVAATPTSLLISWRAQLSPSFYYRITYGETGGNSPV leader and modified C- QEFTVPNDVMTATISGLKPGVDYTITVYAVTTHGVYFYSPISINYR terminus including PC + TPCHHHHHH his tag 106 ADX-5417_E01-Mal- GVSDVPRDLEVVAATPTSLLISWSYDGPIDRYYRITYGETGGNSPV DBCO-FFPF18 QEFTVPPDQKTATISGLKPGVDYTITVYAVRLEEAHYNREFPISIN YRTPC-[Maleamide-DBCO-FFP(18F)] 107 ADX-5417_E01 full length  MGVSDVPRDLEVVAATPTSLLISWRAQLSPSFYYRITYGETGGNSP VQEFTVPNDVMTATISGLKPGVDYTITVYAVTTHGVYFYSPISINY RTPCHHHHHH 108 ADX-5417_E01-core GAAGTGGTTGCTGCCACCCCCACCAGCCTGCTGATCAGCTGGAGGG (nucleotide sequence) CTCAGCTGTCTCCGTCTTTCTATTACCGCATCACTTACGGCGAAAC AGGAGGCAATAGCCCTGTCCAGGAGTTCACTGTGCCTAATGATGTA ATGACAGCTACCATCAGCGGCCTTAAACCTGGCGTTGATTATACCA TCACTGTGTATGCTGTCACTACTCATGGTGTTTATTTCTACTCACC AATTTCCATTAATTACCGCACA 109 ADX_5417_E01 w/ N ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA leader (nucleotide CCCCCACCAGCCTGCTGATCAGCTGGAGGGCTCAGCTGTCTCCGTC sequence with N-terminal TTTCTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT methionine) GTCCAGGAGTTCACTGTGCCTAATGATGTAATGACAGCTACCATCA GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CACTACTCATGGTGTTTATTTCTACTCACCAATTTCCATTAATTAC CGCACA 110 ADX_5417_E01 w/ N ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA leader and modified C- CCCCCACCAGCCTGCTGATCAGCTGGAGGGCTCAGCTGTCTCCGTC terminus including PC TTTCTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT (nucleotide sequence with  GTCCAGGAGTTCACTGTGCCTAATGATGTAATGACAGCTACCATCA N-terminal methionine) GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CACTACTCATGGTGTTTATTTCTACTCACCAATTTCCATTAATTAC CGCACACCGTGC 111 ADX_5417_E01 w/ N ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCA leader and C tail +  CCCCCACCAGCCTGCTGATCAGCTGGAGGGCTCAGCTGTCTCCGTC his tag (nucleotide   TTTCTATTACCGCATCACTTACGGCGAAACAGGAGGCAATAGCCCT sequence with GTCCAGGAGTTCACTGTGCCTAATGATGTAATGACAGCTACCATCA N-terminal methionine) GCGGCCTTAAACCTGGCGTTGATTATACCATCACTGTGTATGCTGT CACTACTCATGGTGTTTATTTCTACTCACCAATTTCCATTAATTAC CGCACACCGTGCCACCATCACCACCACCACTGA 112 ATI_1420_A10 core EVVAATPTSLLISWPYPSYYIEYRITYGETGGNSPVQEFTVQSMKA TISGLKPGVDYTITVYAIRHPGMLEFGISINYRT 113 ATI_1420_A10 BC loop PYPSYYIE 114 ATI_1420_A10 DE loop IRHPGMLEFG 115 ATI_1420_A10 FG loop VTDGASIASYAFP  116 ATI_1420_A10 w/ N GVSDVPRDLEVVAATPTSLLISWPYPSYYIEYRITYGETGGNSPVQ leader EFTVQSMKATISGLKPGVDYTITVYAIRHPGMLEFGISINYRT 117 ATI_1420_A10 w/ N GVSDVPRDLEVVAATPTSLLISWPYPSYYIEYRITYGETGGNSPVQ leader + his tag EFTVQSMKATISGLKPGVDYTITVYAIRHPGMLEFGISINYRTHHH HHH 118 ATI_1420_A10 w/ N GVSDVPRDLEVVAATPTSLLISWPYPSYYIEYRITYGETGGNSPVQ leader and C tail EFTVQSMKATISGLKPGVDYTITVYAIRHPGMLEFGISINYRTEID KPSQ 119 ATI_1420 AlOw/ N leader GVSDVPRDLEVVAATPTSLLISWPYPSYYIEYRITYGETGGNSPVQ and C tail + his tag EFTVQSMKATISGLKPGVDYTITVYAIRHPGMLEFGISINYRTEID KPSQHHHHHH 120 ATI_1420 AlOw/ N leader GVSDVPRDLEVVAATPTSLLISWPYPSYYIEYRITYGETGGNSPVQ and modified C-terminus EFTVQSMKATISGLKPGVDYTITVYAIRHPGMLEFGISINYRTPC including PC 121 ATI_1420_A10 w/ N GVSDVPRDLEVVAATPTSLLISWPYPSYYIEYRITYGETGGNSPVQ leader and modified C- EFTVQSMKATISGLKPGVDYTITVYAIRHPGMLEFGISINYRTPCH terminus including PC + HHHHH his tag 122 ATI_1420_A10-full MGVSDVPRDLEVVAATPTSLLISWPYPSYYIEYRITYGETGGNSPV length QEFTVQSMKATISGLKPGVDYTITVYAIRHPGMLEFGISINYRTEI DKPSQHHHHHH 123 ATI_1420_B09core EVVAATPTSLLISWHKFSSLMSYRITYGETGGNSPVQEFTVGSV NATISGLKPGVDYTITVYAIHNVGFISINYRT 124 ATI_1420_B09 BC loop HKFSSLMS 125 ATI_1420_B09 DE loop GSVN 126 ATI_1420_B09 FG loop IHNVGF 127 ATI_1420_B09 w/ N GVSDVPRDLEVVAATPTSLLISWHKFSSLMSYRITYGETGGNSP  leader VQEFTVGSVNATISGLKPGVDYTITVYAIHNVGFISINYRT 128 ATI_1420_B09 w/ N GVSDVPRDLEVVAATPTSLLISWHKFSSLMSYRITYGETGGNSP  leader + his tag VQEFTVGSVNATISGLKPGVDYTITVYAIHNVGFISINYRTHHH HHH 129 AATI_1420_B09 w/ N GVSDVPRDLEVVAATPTSLLISWHKFSSLMSYRITYGETGGNSP  leader and C tail VQEFTVGSVNATISGLKPGVDYTITVYAIHNVGFISINYRTEID KPSQ 130 ATI_1420_B09 w/ N GVSDVPRDLEVVAATPTSLLISWHKFSSLMSYRITYGETGGNSP  leader and C tail + his tag VQEFTVGSVNATISGLKPGVDYTITVYAIHNVGFISINYRTEID KPSQHHHHHH 131 ATI_1420_B09 w/ N GVSDVPRDLEVVAATPTSLLISWHKFSSLMSYRITYGETGGNSP  leader and modified C- VQEFTVGSVNATISGLKPGVDYTITVYAIHNVGFISINYRTPC terminus including PC 132 ATI_1420_B09 w/ N GVSDVPRDLEVVAATPTSLLISWHKFSSLMSYRITYGETGGNSP  leader and modified C- VQEFTVGSVNATISGLKPGVDYTITVYAIHNVGFISINYRTPCH terminus including PC + HHHHH his tag 133 ATI_1420_B09-full MGVSDVPRDLEVVAATPTSLLISWHKFSLMSYRITYGETGGNS length PVQEFTVGSVNATISGLKPGVDYTITVYAIHNVGFISINYRTEI  DKPSQHHHHHH 134 ATI_1420_C02core EVVAATPTSLLISWRIKSYYAYRITYGETGGNSPVQEFTVRQHV ATISGLKPGVDYTITVYARLGDVELVYEISINYRT 135 ATI_1420_C02 BC loop RIKSYYA 136 ATI_1420_C02 DE loop RQHV 137 ATI_1420_C02 FG loop RLGDVELVYE 138 ATI_1420_C02 w/ N GVSDVPRDLEVVAATPTSLLISWRIKSYYAYRITYGETGGNSPV leader QEFTVRQHVATISGLKPGVDYTITVYARLGDVELVYEISINYRT 139 ATI_1420_C02 w/ N GVSDVPRDLEVVAATPTSLLISWHKFSSLMSYRITYGETGGNSP  leader + his tag VQEFTVGSVNATISGLKPGVDYTITVYAIHNVGFISINYRTHHH HHH 140 ATI_1420_C02 w/ N GVSDVPRDLEVVAATPTSLLISWRIKSYYAYRITYGETGGNSPV leader and C tail QEFTVRQHVATISGLKPGVDYTITVYARLGDVELVYEISINYRT EIDKPSQ 141 ATI_1420_C02 w/ N GVSDVPRDLEVVAATPTSLLISWRIKSYYAYRITYGETGGNSPV leader and C tail + his tag QEFTVRQHVATISGLKPGVDYTITVYARLGDVELVYEISINYRT EIDKPSQHHHHHH 142 ATI_1420_C02 w/ N GVSDVPRDLEVVAATPTSLLISWRIKSYYAYRITYGETGGNSPV leader and modified C- QEFTVRQHVATISGLKPGVDYTITVYARLGDVELVYEISINYRT terminus including PC PC 143 ATI_1420_C02 w/ N GVSDVPRDLEVVAATPTSLLISWHKFSSLMSYRITYGETGGNSP  leader and modified C- VQEFTVGSVNATISGLKPGVDYTITVYAIHNVGFISINYRTPCH terminus including PC + HHHHH his tag 144 ATI_1420_C02-full MGVSDVPRDLEVVAATPTSLLISWRIKSYYAYRITYGETGGNSP  length VQEFTVRQHVATISGLKPGVDYTITVYARLGDVELVYEISINYR TEIDKPSQHHHHHH 145 ATI_1420_C11 core EVVAATPTSLLISWMYPLKSVPYRITYGETGGNSPVQEFTVYSS GATISGLKPGVDYTITVYAMSYSTYHAFMISINYRT 146 ATI_1420_C11 BC loop MYPLKSVP  147 ATI_1420_C11 DE loop YSG 148 ATI_1420_C11 FG loop MSYSTYHAFM 149 ATI_1420_C11 w/ N leader GVSDVPRDLEVVAATPTSLLISWMYPLKSVPYRITYGETGGNSP  VQEFTVYSGATISGLKPGVDYTITVYAMSYSTYHAFMISINYR T 150 ATI_1420_C11 w/ N leader + GVSDVPRDLEVVAATPTSLLISWMYPLKSVPYRITYGETGGNSP  his tag VQEFTVYSGATISGLKPGVDYTITVYAMSYSTYHAFMISINYR THHHHHH 151 ATI_1420_C11 w/ N leader GVSDVPRDLEVVAATPTSLLISWMYPLKSVPYRITYGETGGNSP  and C tail VQEFTVYSGATISGLKPGVDYTITVYAMSYSTYHAFMISINYR TEIDKPSQ 152 ATI_1420_C11 w/ N leader GVSDVPRDLEVVAATPTSLLISWMYPLKSVPYRITYGETGGNSP  and C tail + his tag VQEFTVYSGATISGLKPGVDYTITVYAMSYSTYHAFMISINYR TEIDKPSQHHHHHH 153 ATI_1420_C11 w/ N leader GVSDVPRDLEVVAATPTSLLISWMYPLKSVPYRITYGETGGNSP  and modified C-terminus VQEFTVYSGATISGLKPGVDYTITVYAMSYSTYHAFMISINYR including PC TPC 154 ATI_1420_C11 w/ N leader GVSDVPRDLEVVAATPTSLLISWMYPLKSVPYRITYGETGGNSP  and modified C-terminus VQEFTVYSGATISGLKPGVDYTITVYAMSYSTYHAFMISINYR including PC + his tag TPCHHHHHH 155 AATI_1420_C11-full MGVSDVPRDLEVVAATPTSLLISWMYPLKSVPYRITYGETGGNS length PVQEFTVYSSGATISGLKPGVDYTITVYAMSYSTYHAFMISINY RTEIDKPSQHHHHHH 156 ATI_1420_D01 core EVVAATPTSLLISWRTVPETDYRITYGETGGNSPVQEFTVPDNT ATISGLKPGVDYTITVYALETAHYNRDYISINYRT 157 ATI_1420_D01 BC loop RTVPETD 158 ATI_1420_D01 DE loop PDNT 159 ATI_1420_D01 FG loop LETAHYNRDY 160 ATI_1420_D01 w/ N GVSDVPRDLEVVAATPTSLLISWRTVPETDYRITYGETGGNSPV leader QEFTVPDNTATISGLKPGVDYTITVYALETAHYNRDYISINYRT 161 ATI_1420_D01 w/ N GVSDVPRDLEVVAATPTSLLISWRTVPETDYRITYGETGGNSPV leader + his tag QEFTVPDNTATISGLKPGVDYTITVYALETAHYNRDYISINYRT HHHHHH 162 ATI_1420_D01 w/ N GVSDVPRDLEVVAATPTSLLISWRTVPETDYRITYGETGGNSPV leader and C tail QEFTVPDNTATISGLKPGVDYTITVYALETAHYNRDYISINYRT EIDKPSQ 163 ATI_1420_D01 w/ N GVSDVPRDLEVVAATPTSLLISWRTVPETDYRITYGETGGNSPV leader and C tail + his tag QEFTVPDNTATISGLKPGVDYTITVYALETAHYNRDYISINYRT EIDKPSQHHHHHH 164 ATI_1420_D01 w/ N GVSDVPRDLEVVAATPTSLLISWRTVPETDYRITYGETGGNSPV leader and modified C- QEFTVPDNTATISGLKPGVDYTITVYALETAHYNRDYISINYRT terminus including PC PC 165 ATI_1420_D01 w/ N GVSDVPRDLEVVAATPTSLLISWRTVPETDYRITYGETGGNSPV leader and modified C- QEFTVPDNTATISGLKPGVDYTITVYALETAHYNRDYISINYRT terminus including PC + PCHHHHHH his tag 166 ATI_1420_D01-full MGVSDVPRDLEVVAATPTSLLISWRTVPETDYRITYGETGGNSP  length VQEFTVPDNTATISGLKPGVDYTITVYALETAHYNRDYISINYR TEIDKPSQHHHHHH 167 ATI_1420_D05 core EVVAATPTSLLISWTAYYSTIKYRITYGETGGNSPVQEFTVGPK HHATISGLKPGVDYTITVYAYNTKPGYHAHQISINYRT 168 ATI_1420_D05 BC loop TAYYSTIK 169 ATI_1420_D05 DE loop GPKHH 170 ATI_1420_D05 FG loop YNTKPGYHAHQ 171 ATI_1420_D05 w/ N GVSDVPRDLEVVAATPTSLLISWTAYYSTIKYRITYGETGGNSP  leader VQEFTVGPKHHATISGLKPGVDYTITVYAYNTKPGYHAHQISIN YRT 172 ATI_1420_D05 w/ N GVSDVPRDLEVVAATPTSLLISWTAYYSTIKYRITYGETGGNSP  leader + his tag VQEFTVGPKHHATISGLKPGVDYTITVYAYNTKPGYHAHQISIN YRTHHHHHH 173 ATI_1420_D05 w/ N GVSDVPRDLEVVAATPTSLLISWTAYYSTIKYRITYGETGGNSP  leader and C tail VQEFTVGPKHHATISGLKPGVDYTITVYAYNTKPGYHAHQISIN YRTEIDKPSQ 174 ATI_1420_D05 w/ N GVSDVPRDLEVVAATPTSLLISWTAYYSTIKYRITYGETGGNSP  leader and C tail + his tag VQEFTVGPKHHATISGLKPGVDYTITVYAYNTKPGYHAHQISIN YRTEIDKPSQHHHHHH 175 ATI_1420_D05 w/ N GVSDVPRDLEVVAATPTSLLISWTAYYSTIKYRITYGETGGNSP  leader and modified C- VQEFTVGPKHHATISGLKPGVDYTITVYAYNTKPGYHAHQISIN terminus including PC YRTPC 176 ATI_1420_D05 w/ N GVSDVPRDLEVVAATPTSLLISWTAYYSTIKYRITYGETGGNSP  leader and modified C- VQEFTVGPKHHATISGLKPGVDYTITVYAYNTKPGYHAHQISIN terminus including PC + YRTPCHHHHHH his tag 177 ATI_1420_D05-full MGVSDVPRDLEVVAATPTSLLISWTAYYSTIKYRITYGETGGNS length PVQEFTVGPKHHATISGLKPGVDYTITVYAYNTKPGYHAHQISI  NYRTEIDKPSQHHHHHH 178 ATI_1420 D10 core EVVAATPTSLLISWRIPSYHIQYRITYGETGGNSPVQEFTVYQK YATISGLKPGVDYTITVYAVSPPKQLRFGISINYRT 179 ATI_1420 D10 BC loop RIPSYHIQ 180 ATI_1420 D10 DE loop YQKY 181 ATI_1420 D10 FG loop VSPPKQLRFG 182 ATI_1420 D10 w/ N GVSDVPRDLEVVAATPTSLLISWRIPSYHIQYRITYGETGGNSP  leader VQEFTVYQKYATISGLKPGVDYTITVYAVSPPKQLRFGISINYR T 183 ATI_1420 D10 w/ N GVSDVPRDLEVVAATPTSLLISWRIPSYHIQYRITYGETGGNSP  leader + his tag VQEFTVYQKYATISGLKPGVDYTITVYAVSPPKQLRFGISINYR THHHHHH 184 ATI_1420 D10 w/ N GVSDVPRDLEVVAATPTSLLISWRIPSYHIQYRITYGETGGNSP  leader and C tail VQEFTVYQKYATISGLKPGVDYTITVYAVSPPKQLRFGISINYR TEIDKPSQ 185 ATI_1420 D10 w/ N GVSDVPRDLEVVAATPTSLLISWRIPSYHIQYRITYGETGGNSP  leader and C tail + his tag VQEFTVYQKYATISGLKPGVDYTITVYAVSPPKQLRFGISINYR TEIDKPSQHHHHHH 186 ATI_1420 D10 w/ N GVSDVPRDLEVVAATPTSLLISWRIPSYHIQYRITYGETGGNSP  leader and modified C- VQEFTVYQKYATISGLKPGVDYTITVYAVSPPKQLRFGISINYR terminus including PC TPC 187 ATI_1420 D10 w/ N GVSDVPRDLEVVAATPTSLLISWRIPSYHIQYRITYGETGGNSP  leader and modified C- VQEFTVYQKYATISGLKPGVDYTITVYAVSPPKQLRFGISINYR terminus including PC + TPCHHHHHH his tag 188 ATI_1420_D010-full MGVSDVPRDLEVVAATPTSLLISWRIPSYHIQYRITYGETGGNS length PVQEFTVYQKYATISGLKPGVDYTITVYAVSPPKQLRFGISINY RTEIDKPSQHHHHHH 189 ATI_1420_F10 core EVVAATPTSLLISWPAPPSYVFYRITYGETGGNSPVQEFTVYPY MATISGLKPGVDYTITVYAYTSGFSISINYRT 190 ATI_1420_F10 BC loop PAPPSYVF 191 ATI_1420_F10 DE loop YPYM 192 ATI_1420_F10 FG loop YTSGFS 193 ATI_1420_F10 w/ N leader GVSDVPRDLEVVAATPTSLLISWPAPPSYVFYRITYGETGGNSP  VQEFTVYPYMATISGLKPGVDYTITVYAYTSGFSISINYRT 194 ATI_1420_F10 w/ N GVSDVPRDLEVVAATPTSLLISWPAPPSYVFYRITYGETGGNSP  leader + his tag VQEFTVYPYMATISGLKPGVDYTITVYAYTSGFSISINYRTHHH HHH 195 ATI_1420_F10 w/ N leader GVSDVPRDLEVVAATPTSLLISWPAPPSYVFYRITYGETGGNSP  and C tail VQEFTVYPYMATISGLKPGVDYTITVYAYTSGFSISINYRTEID KPSQ 196 ATI_1420_F10 w/ N GVSDVPRDLEVVAATPTSLLISWPAPPSYVFYRITYGETGGNSP  leader and C tail + his tag VQEFTVYPYMATISGLKPGVDYTITVYAYTSGFSISINYRTEID KPSQHHHHHH 197 ATI_1420_F10 w/ N GVSDVPRDLEVVAATPTSLLISWPAPPSYVFYRITYGETGGNSP  leader and modified C- VQEFTVYPYMATISGLKPGVDYTITVYAYTSGFSISINYRTPC terminus including PC 198 ATI_1420_F10 w/ N GVSDVPRDLEVVAATPTSLLISWPAPPSYVFYRITYGETGGNSP  leader and modified C- VQEFTVYPYMATISGLKPGVDYTITVYAYTSGFSISINYRTPCH terminus including PC + HHHHH his tag 199 ATI_1420_F10-full length  MGVSDVPRDLEVVAATPTSLLISWPAPPSYVFYRITYGETGGNS PVQEFTVYPYMATISGLKPGVDYTITVYAYTSGFSISINYRTEI  DKPSQHHHHHH 200 ATI_1421_C05 core EVVAATPTSLLISWYMDHKSKYRITYGETGGNSPVQEFTVPDQR ATISGLKPGVDYTITVYALSEAHYLRDKISINYRT 201 ATI_1421_C05 BC loop YMDHKSK 202 ATI_1421_C05 DE loop PDQR 203 ATI_1421_C05 FG loop LSEAHYLRDK 204 ATI_1421_C05 w/ N GVSDVPRDLEVVAATPTSLLISWYMDHKSKYRITYGETGGNSPV leader QEFTVPDQRATISGLKPGVDYTITVYALSEAHYLRDKISINYRT 205 ATI_1421_C05 w/ N GVSDVPRDLEVVAATPTSLLISWYMDHKSKYRITYGETGGNSPV leader + his tag QEFTVPDQRATISGLKPGVDYTITVYALSEAHYLRDKISINYRT HHHHHH 206 ATI_1421_C05 w/ N GVSDVPRDLEVVAATPTSLLISWYMDHKSKYRITYGETGGNSPV leader and C tail QEFTVPDQRATISGLKPGVDYTITVYALSEAHYLRDKISINYRT EIDKPSQ 207 ATI_1421_C05 w/ N GVSDVPRDLEVVAATPTSLLISWYMDHKSKYRITYGETGGNSPV leader and C tail + his tag QEFTVPDQRATISGLKPGVDYTITVYALSEAHYLRDKISINYRT EIDKPSQHHHHHH 208 ATI_1421_C05 w/ N GVSDVPRDLEVVAATPTSLLISWYMDHKSKYRITYGETGGNSPV leader and modified C- QEFTVPDQRATISGLKPGVDYTITVYALSEAHYLRDKISINYRT terminus including PC PC 209 ATI_1421_C05 w/ N GVSDVPRDLEVVAATPTSLLISWYMDHKSKYRITYGETGGNSPV leader and modified C- QEFTVPDQRATISGLKPGVDYTITVYALSEAHYLRDKISINYRT terminus including PC + PCHHHHHH his tag 210 ATI_1421_C05-full MGVSDVPRDLEVVAATPTSLLISWYMDHKSKYRITYGETGGNSP  length VQEFTVPDQRATISGLKPGVDYTITVYALSEAHYLRDKISINYR TEIDKPSQHHHHHH 211 ATI_1421_C06 core EVVAATPTSLLISWENLASYQYRITYGETGGNSPVQEFTVPDQA ATISGLKPGVDYTITVYALQTAHYYRQHISINYRT 212 ATI_1421_C06 BC loop ENLASYQ 213 ATI_1421_C06DE loop PDQA 214 ATI_1421_C06FG loop LQTAHYYRQH 215 ATI_1421_C06 w/ N GVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSPV leader QEFTVPDQAATISGLKPGVDYTITVYALQTAHYYRQHISINYRT 216 ATI_1421_C06 w/ N GVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSPV leader + his tag QEFTVPDQAATISGLKPGVDYTITVYALQTAHYYRQHISINYRT HHHHHH 217 ATI_1421_C06w/ N leader GVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSPV and C tail QEFTVPDQAATISGLKPGVDYTITVYALQTAHYYRQHISINYRT EIDKPSQ 218 ATI_1421_C06 w/ N GVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSPV leader and C tail + his tag QEFTVPDQAATISGLKPGVDYTITVYALQTAHYYRQHISINYRT EIDKPSQHHHHHH 219 ATI_1421_C06 w/ N GVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSPV leader and modified C- QEFTVPDQAATISGLKPGVDYTITVYALQTAHYYRQHISINYRT terminus including PC PC 220 ATI_1421_C06 w/ N GVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSPV leader and modified C- QEFTVPDQAATISGLKPGVDYTITVYALQTAHYYRQHISINYRT terminus including PC + PCHHHHHH his tag 221 ATI_1421_C06-full MGVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSP  length VQEFTVPDQAATISGLKPGVDYTITVYALQTAHYYRQHISINYR TEIDKPSQHHHHHH 222 ATI_1421_DOS core EVVAATPTSLLISWYYVQYNDYRITYGETGGNSPVQEFTVPDQS ATISGLKPGVDYTITVYALEKAHYYRQNISINYRT 223 ATI_1421_D05 BC loop YYVQYND 224 ATI_1421_D05 DE loop PDQS 225 ATI_1421_D05 FG loop LEKAHYYRQN 226 ATI_1421_D05 w/ N leader GVSDVPRDLEVVAATPTSLLISWYYVQYNDYRITYGETGGNSPV QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT 227 ATI_1421_D05 w/ N leader GVSDVPRDLEVVAATPTSLLISWYYVQYNDYRITYGETGGNSPV + his tag QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT HHHHHH 228 ATI_1421_D05 w/ N leader GVSDVPRDLEVVAATPTSLLISWYYVQYNDYRITYGETGGNSPV and C tail QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT EIDKPSQ 229 ATI_1421_D05 w/ N leader GVSDVPRDLEVVAATPTSLLISWYYVQYNDYRITYGETGGNSPV and C tail + his tag QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT EIDKPSQHHHHHH 230 ATI_1421_D05 w/ N leader GVSDVPRDLEVVAATPTSLLISWYYVQYNDYRITYGETGGNSPV and modified C-terminus QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT including PC PC 231 ATI_1421_D05 w/ N leader GVSDVPRDLEVVAATPTSLLISWYYVQYNDYRITYGETGGNSPV and modified C-terminus QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT including PC + his tag PCHHHHHH 232 ATI_1421_D05-full MGVSDVPRDLEVVAATPTSLLISWYYVQYNDYRITYGETGGNSP  length VQEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYR TEIDKPSQHHHHHH 233 ATI_1421_D06 core EVVAATPTSLLISWGHNYDDEYRITYGETGGNSPVQEFTVPDQY ATISGLKPGVDYTITVYALAEAHVRKNHISINYRT 234 ATI_1421_D06 BC loop GHNYDDE 235 ATI_1421_D06 DE loop PDQY 236 ATI_1421_D06 FG loop LAEAHVRKNH 237 ATI_1421_D06 w/ N GVSDVPRDLEVVAATPTSLLISWGHNYDDEYRITYGETGGNSPV leader QEFTVPDQYATISGLKPGVDYTITVYALAEAHVRKNHISINYRT 238 ATI_1421_D06 w/ N GVSDVPRDLEVVAATPTSLLISWGHNYDDEYRITYGETGGNSPV leader + his tag QEFTVPDQYATISGLKPGVDYTITVYALAEAHVRKNHISINYRT HHHHHH 239 ATI_1421_D06 w/ N GVSDVPRDLEVVAATPTSLLISWGHNYDDEYRITYGETGGNSPV leader and C tail QEFTVPDQYATISGLKPGVDYTITVYALAEAHVRKNHISINYRT EIDKPSQ 240 ATI_1421_D06 w/ N GVSDVPRDLEVVAATPTSLLISWGHNYDDEYRITYGETGGNSPV leader and C tail + his tag QEFTVPDQYATISGLKPGVDYTITVYALAEAHVRKNHISINYRT EIDKPSQHHHHHH 241 ATI_1421_D06 w/ N GVSDVPRDLEVVAATPTSLLISWGHNYDDEYRITYGETGGNSPV leader and modified C- QEFTVPDQYATISGLKPGVDYTITVYALAEAHVRKNHISINYRT terminus including PC PC 242 ATI_1421_D06 w/ N GVSDVPRDLEVVAATPTSLLISWGHNYDDEYRITYGETGGNSPV leader and modified C- QEFTVPDQYATISGLKPGVDYTITVYALAEAHVRKNHISINYRT terminus including PC + PCHHHHHH his tag 243 ATI_1421_D06-full MGVSDVPRDLEVVAATPTSLLISWGHNYDDEYRITYGETGGNSP  length VQEFTVPDQYATISGLKPGVDYTITVYALAEAHVRKNHISINYR TEIDKPSQHHHHHH 244 ATI_1421_E03 core EVVAATPTSLLISWVYHYDAQYRITYGETGGNSPVQEFTVPDQK ATISGLKPGVDYTITVYALSEAHHKRDSISINYRT 245 ATI_1421_E03 BC loop VYHYDAQ 246 ATI_1421_E03 DE loop PDQK 247 ATI_1421_E03 FG loop LSEAHHKRDS 248 ATI_1421_E03 w/ N leader GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT HHHHHH 249 ATI_1421_E03w/ N leader + GvsavpRDLEvvAATPTsLLiswvyHyDAQYRITYGETGGNsPv his tag QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT EIDKPSQ 250 ATI_1421_E03w/ N leader GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV and C tail QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT EIDKPSQHHHHHH 251 ATI_1421_E03 w/ N leader GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV and C tail + his tag QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT PC 252 ATI_1421_E03 w/ N leader GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV and modified C-terminus QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT including PC PCHHHHHH 253 ATI_1421_E03 w/ N leader GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV and modified C-terminus QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT including PC + his tag 254 ATI_1421_E03-full MGVSDVPRDLEVVAATPTS LLISWVYHYDAQYRITYGETGGNSP  length VQEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYR TEIDKPSQHHHHHH 255 ATI_1421_E04 core EVVAATPTSLLISWSYNGPIEYRITYGETGGNSPVQEFTVPDQQ ATISGLKPGVDYTITVYALEEAHYSRQSISINYRT 256 ATI_1421_E04 BC loop SYNGPIE 257 ATI_1421_E04 DE loop PDQQ 258 ATI_1421_E04 FG loop LEEAHYSRQS 259 ATI_1421_E04 w/ N leader GVSDVPRDLEVVAATPTSLLISWSYNGPIEYRITYGETGGNSPV QEFTVPDQQATISGLKPGVDYTITVYALEEAHYSRQSISINYRT 260 ATI_1421_E04 w/ N leader + GVSDVPRDLEVVAATPTSLLISWSYNGPIEYRITYGETGGNSPV his tag QEFTVPDQQATISGLKPGVDYTITVYALEEAHYSRQSISINYRT HHHHHH 261 ATI_1421_E04 w/ N GVSDVPRDLEVVAATPTSLLISWSYNGPIEYRITYGETGGNSPV leader and C tail QEFTVPDQQATISGLKPGVDYTITVYALEEAHYSRQSISINYRT EIDKPSQ 262 ATI_1421_E04 w/ N leader GVSDVPRDLEVVAATPTSLLISWSYNGPIEYRITYGETGGNSPV and C tail + his tag QEFTVPDQQATISGLKPGVDYTITVYALEEAHYSRQSISINYRT EIDKPSQHHHHHH 263 ATI_1421_E04 w/ N leader GVSDVPRDLEVVAATPTSLLISWSYNGPIEYRITYGETGGNSPV and modified C-terminus QEFTVPDQQATISGLKPGVDYTITVYALEEAHYSRQSISINYRT including PC PC 264 ATI_1421_E04 w/ N leader GVSDVPRDLEVVAATPTSLLISWSYNGPIEYRITYGETGGNSPV and modified C-terminus QEFTVPDQQATISGLKPGVDYTITVYALEEAHYSRQSISINYRT including PC + his tag PCHHHHHH 265 ATI_1421_E04-full length MGVSDVPRDLEVVAATPTSLLISWSYNGPIEYRITYGETGGNSP  VQEFTVPDQQATISGLKPGVDYTITVYALEEAHYSRQSISINYR TEIDKPSQHHHHHH 266 ATI_1421_F03 core EVVAATPTSLLISWISVQTYDYRITYGETGGNSPVQEFTVPDQS ATISGLKPGVDYTITVYALEKAHYYRQNISINYRT 267 ATI_1421_F03 BC loop ISVQTYD 268 ATI_1421_F03 DE loop PDQS 269 ATI_1421_F03 FG loop LEKAHYYRQN 270 ATI_1421_F03 w/ N leader GVSDVPRDLEVVAATPTSLLISWISVQTYDYRITYGETGGNSPV QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT 271 ATI_1421_F03 w/ N leader + GVSDVPRDLEVVAATPTSLLISWISVQTYDYRITYGETGGNSPV his tag QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT HHHHHH 272 ATI_1421_F03 w/ N GVSDVPRDLEVVAATPTSLLISWISVQTYDYRITYGETGGNSPV leader and C tail QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT EIDKPSQ 273 ATI_1421_F03 w/ N leader GVSDVPRDLEVVAATPTSLLISWISVQTYDYRITYGETGGNSPV and C tail + his tag QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT EIDKPSQHHHHHH 274 ATI_1421_F03 w/ N leader GVSDVPRDLEVVAATPTSLLISWISVQTYDYRITYGETGGNSPV and modified C-terminus QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT including PC PC 275 ATI_1421_F03 w/ N leader GVSDVPRDLEVVAATPTSLLISWISVQTYDYRITYGETGGNSPV and modified C-terminus QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT including PC + his tag PCHHHHHH 276 ATI_1421_F03-full length  MGVSDVPRDLEVVAATPTSLLISWISVQTYDYRITYGETGGNSP  VQEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYR TEIDKPSQHHHHHH 277 ATI_1421_F05 core EVVAATPTSLLISWLARHDARYRITYGETGGNSPVQEFTVPDRM ATISGLKPGVDYTITVYALEQAHYYRLYISINYRT 278 ATI_1421_F05 BC loop LARHDAR 279 ATI_1421_F05 DE loop PDRM 280 ATI_1421_F05 FG loop LEQAHYYRLY 281 ATI_1421_F05 w/ N leader GVSDVPRDLEVVAATPTSLLISWLARHDARYRITYGETGGNSPV QEFTVPDRMATISGLKPGVDYTITVYALEQAHYYRLYISINYRT 282 ATI_1421_F05 w/ N leader + GVSDVPRDLEVVAATPTSLLISWLARHDARYRITYGETGGNSPV his tag QEFTVPDRMATISGLKPGVDYTITVYALEQAHYYRLYISINYRT HHHHHH 283 ATI_1421_F05 w/ N leader GVSDVPRDLEVVAATPTSLLISWLARHDARYRITYGETGGNSPV and C tail QEFTVPDRMATISGLKPGVDYTITVYALEQAHYYRLYISINYRT EIDKPSQ 284 ATI_1421_F05 w/ N leader GVSDVPRDLEVVAATPTSLLISWLARHDARYRITYGETGGNSPV and C tail + his tag QEFTVPDRMATISGLKPGVDYTITVYALEQAHYYRLYISINYRT EIDKPSQHHHHHH 285 ATI_1421_F05 w/ N leader GVSDVPRDLEVVAATPTSLLISWLARHDARYRITYGETGGNSPV and modified C-terminus QEFTVPDRMATISGLKPGVDYTITVYALEQAHYYRLYISINYRT including PC PC 286 ATI_1421_F05 w/ N leader GVSDVPRDLEVVAATPTSLLISWLARHDARYRITYGETGGNSPV and modified C-terminus QEFTVPDRMATISGLKPGVDYTITVYALEQAHYYRLYISINYRT including PC + his tag PCHHHHHH 287 ATI_1421_F05-full length  MGVSDVPRDLEVVAATPTS LLISWLARHDARYRITYGETGGNSP  VQEFTVPDRMATISGLKPGVDYTITVYALEQAHYYRLYISINYR TEIDKPSQHHHHHH 288 ATI_1421_G07 core EVVAATPTSLLISWHSPTSGITYRITYGETGGNSPVQEFTVPYD PSATISGLKPGVDYTITVYAPYGSQYYPGYHISINYRT 289 ATI_1421_G07 BC loop HSPTSGIT 290 ATI_1421_G07 DE loop PYDPS 291 ATI_1421_G07 FG loop PYGSQYYPGYH 292 ATI_1421_G07 w/ N GVSDVPRDLEVVAATPTSLLISWHSPTSGITYRITYGETGGNSP  leader VQEFTVPYDPSATISGLKPGVDYTITVYAPYGSQYYPGYHISIN YRT 293 ATI_1421_G07 w/ N GVSDVPRDLEVVAATPTSLLISWHSPTSGITYRITYGETGGNSP  leader + his tag VQEFTVPYDPSATISGLKPGVDYTITVYAPYGSQYYPGYHISIN YRTHHHHHH 294 ATI_1421_G07 w/ N GVSDVPRDLEVVAATPTSLLISWHSPTSGITYRITYGETGGNSP  leader and C tail VQEFTVPYDPSATISGLKPGVDYTITVYAPYGSQYYPGYHISIN YRTEIDKPSQ 295 ATI_1421_G07 w/ N GVSDVPRDLEVVAATPTSLLISWHSPTSGITYRITYGETGGNSP  leader and C tail +  VQEFTVPYDPSATISGLKPGVDYTITVYAPYGSQYYPGYHISIN his tag YRTEIDKPSQHHHHHH 296 ATI_1421_G07 w/ N GVSDVPRDLEVVAATPTSLLISWHSPTSGITYRITYGETGGNSP  leader and modified C- VQEFTVPYDPSATISGLKPGVDYTITVYAPYGSQYYPGYHISIN terminus including PC YRTPC 297 ATI_1421_G07 w/ N GVSDVPRDLEVVAATPTSLLISWHSPTSGITYRITYGETGGNSP  leader and modified C- VQEFTVPYDPSATISGLKPGVDYTITVYAPYGSQYYPGYHISIN terminus including PC + YRTPCHHHHHH his tag 298 ATI_1421_G07-full MGVSDVPRDLEVVAATPTSLLISWHSPTSGITYRITYGETGGNS length PVQEFTVPYDPSATISGLKPGVDYTITVYAPYGSQYYPGYHISI  NYRTEIDKPSQHHHHHH 299 ATI_1421_H03 core EVVAATPTSLLISWVYHYDAQYRITYGETGGNSPVQEFTVPDSS ATISGLKPGVDYTITVYALEQAHIDRTTISINYRT 300 ATI_1421_H03 BC loop VYHYDAQ 301 ATI_1421_H03 DE loop PDS 302 ATI_1421_H03 FG loop LEQAHIDRTT 303 ATI_1421_H03 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV leader QEFTVPDSATISGLKPGVDYTITVYALEQAHIDRTTISINYRT 304 ATI_1421_H03 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV leader + his tag QEFTVPDSATISGLKPGVDYTITVYALEQAHIDRTTISINYRT HHHHHH 305 ATI_1421_H03 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV leader and C tail QEFTVPDSATISGLKPGVDYTITVYALEQAHIDRTTISINYRT EIDKPSQ 306 ATI_1421_H03 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV leader and C tail + his tag QEFTVPDSATISGLKPGVDYTITVYALEQAHIDRTTISINYRT EIDKPSQHHHHHH 307 ATI_1421_H03 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV leader and modified C- QEFTVPDSATISGLKPGVDYTITVYALEQAHIDRTTISINYRT terminus including PC PC 308 ATI_1421_H03 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV leader and modified C- QEFTVPDSATISGLKPGVDYTITVYALEQAHIDRTTISINYRT terminus including PC + PCHHHHHH his tag 309 ATI_1421_H03-full MGVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSP  length VQEFTVPDSATISGLKPGVDYTITVYALEQAHIDRTTISINYR TEIDKPSQHHHHHH 310 ATI_1421_H05 core EVVAATPTSLLISWTSVLLKDYRITYGETGGNSPVQEFTVPDQH ATISGLKPGVDYTITVYALQNAHHERLYISINYRT 311 ATI_1421_H05 BC loop TSVLLKD 312 ATI_1421_H05 DE loop PDQH 313 ATI_1421_H05 FG loop LQNAHHERLY 314 ATI_1421_H05 w/ N GVSDVPRDLEVVAATPTSLLISWTSVLLKDYRITYGETGGNSPV leader QEFTVPDQHATISGLKPGVDYTITVYALQNAHHERLYISINYRT 315 ATI_1421_H05 w/ N GVSDVPRDLEVVAATPTSLLISWTSVLLKDYRITYGETGGNSPV leader + his tag QEFTVPDQHATISGLKPGVDYTITVYALQNAHHERLYISINYRT HHHHHH 316 ATI_1421_H05 w/ N GVSDVPRDLEVVAATPTSLLISWTSVLLKDYRITYGETGGNSPV leader and C tail QEFTVPDQHATISGLKPGVDYTITVYALQNAHHERLYISINYRT EIDKPSQ 317 ATI_1421_H05 w/ N GVSDVPRDLEVVAATPTSLLISWTSVLLKDYRITYGETGGNSPV leader and C tail + his tag QEFTVPDQHATISGLKPGVDYTITVYALQNAHHERLYISINYRT EIDKPSQHHHHHH 318 ATI_1421_H05 w/ N GVSDVPRDLEVVAATPTSLLISWTSVLLKDYRITYGETGGNSPV leader and modified C- QEFTVPDQHATISGLKPGVDYTITVYALQNAHHERLYISINYRT terminus including PC PC 319 ATI_1421_H05 w/ N GVSDVPRDLEVVAATPTSLLISWTSVLLKDYRITYGETGGNSPV leader and modified C- QEFTVPDQHATISGLKPGVDYTITVYALQNAHHERLYISINYRT terminus including PC + PCHHHHHH his tag 320 ATI_1421_H05-full MGVSDVPRDLEVVAATPTSLLISWTSVLLKDYRITYGETGGNSP  length VQEFTVPDQHATISGLKPGVDYTITVYALQNAHHERLYISINYR TEIDKPSQHHHHHH 321 ATI_1422_E06 core EVVAATPTSLLISWLPSYYITYRITYGETGGNSPVQEFTVSKDL ATISGLKPGVDYTITVYAFNGSYYTFGISINYRT 322 ATI_1422_E06 BC loop LPSYYIT 323 ATI_1422_E06 DE loop SKDL 324 ATI_1422_E06 FG loop FNGSSYYTFG 325 ATI_1422_E06 w/ N leader GVSDVPRDLEVVAATPTSLLISWLPSYYITYRITYGETGGNSPV QEFTVSKDLATISGLKPGVDYTITVYAFNGSYYTFGISINYRT 326 ATI_1422_E06 w/ N leader + GVSDVPRDLEVVAATPTSLLISWLPSYYITYRITYGETGGNSPV his tag QEFTVSKDLATISGLKPGVDYTITVYAFNGSYYTFGISINYRT EIDKPSQHHHHHH 327 ATI_1422_E06 w/ N leader GvsavpRDLEvvAATPTsLLISWLPSYYITYRITYGETGGNSPV and C tail QEFTVSKDLATISGLKPGVDYTITVYAFNGSYYTFGISINYRT EIDKPSQHHHHHH 328 ATI_1422_E06 w/ N leader GVSDVPRDLEVVAATPTSLLISWLPSYYITYRITYGETGGNSPV and C tail + his tag QEFTVSKDLATISGLKPGVDYTITVYAFNGSYYTFGISINYRT PC 329 ATI_1422_E06 w/ N leader GvsavpRDLEvvAATPTsLLISWLPSYYITYRITYGETGGNSPV and modified C-terminus QEFTVSKDLATISGLKPGVDYTITVYAFNGSYYTFGISINYRT including PC PCHHHHHH 330 ATI_1422_E06 w/ N leader GVSDVPRDLEVVAATPTSLLISWLPSYYITYRITYGETGGNSPV and modified C-terminus QEFTVSKDLATISGLKPGVDYTITVYAFNGSYYTFGISINYRT including PC + his tag EIDKPSQHHHHHH 331 ATI_1422_E06-full length  MGVSDVPRDLEVVAATPTSLLISWLPSYYITYRITYGETGGNSP  VQEFTVSKDLATISGLKPGVDYTITVYAFNGSYYTFGISINYR T 332 ATI_1422_F04 core EVVAATPTSLLISWSIPSYFISYRITYGETGGNSPVQEFTVYKN YATISGLKPGVDYTITVYASEGIMFYNISINYRT 333 ATI_1422_F04 BC loop SIPSYFIS 334 ATI_1422_F04 DE loop YKNY 335 ATI_1422_F04 FG loop SEGIMFYN 336 ATI_1422_F04w/ N leader GVSDVPRDLEVVAATPTSLLISWSIPSYFISYRITYGETGGNSP  VQEFTVYKNYATISGLKPGVDYTITVYASEGIMFYNISINYRT 337 ATI_1422_F04w/ N leader + GVSDVPRDLEVVAATPTSLLISWSIPSYFISYRITYGETGGNSP  his tag VQEFTVYKNYATISGLKPGVDYTITVYASEGIMFYNISINYRTH HHHHH 338 ATI_1422_F04 w/ N GVSDVPRDLEVVAATPTSLLISWSIPSYFISYRITYGETGGNSP  leader and C tail VQEFTVYKNYATISGLKPGVDYTITVYASEGIMFYNISINYRTE IDKPSQ 339 ATI_1422_F04 w/ N leader GVSDVPRDLEVVAATPTSLLISWSIPSYFISYRITYGETGGNSP  and C tail + his tag VQEFTVYKNYATISGLKPGVDYTITVYASEGIMFYNISINYRTE IDKPSQHHHHHH 340 ATI_1422_F04 w/ N leader GVSDVPRDLEVVAATPTSLLISWSIPSYFISYRITYGETGGNSP  and modified C-terminus VQEFTVYKNYATISGLKPGVDYTITVYASEGIMFYNISINYRTP  including PC C 341 ATI_1422_F04 w/ N leader GVSDVPRDLEVVAATPTSLLISWSIPSYFISYRITYGETGGNSP  and modified C-terminus VQEFTVYKNYATISGLKPGVDYTITVYASEGIMFYNISINYRTP  including PC + his tag CHHHHHH 342 ATI_1422_F04-full length MGVSDVPRDLEVVAATPTSLLISWSIPSYFISYRITYGETGGNS PVQEFTVYKNYATISGLKPGVDYTITVYASEGIMFYNISINYRT EIDKPSQHHHHHH 343 ATI_1422_F05 core EVVAATPTSLLISWPYPRGPYVFYRITYGETGGNSPVQEFTVYP  GQATISGLKPGVDYTITVYAYTSGYVISINYRT 344 ATI_1422_F05 BC loop PYPRGPYVF 345 ATI_1422_F05 DE loop YPGQ 346 ATI_1422_F05 FG loop YTSGYV 347 ATI_1422_F05 w/ N leader GVSDVPRDLEVVAATPTSLLISWPYPRGPYVFYRITYGETGGNS PVQEFTVYPGQATISGLKPGVDYTITVYAYTSGYVISINYRT 348 ATI_1422_F05 w/ N leader + GVSDVPRDLEVVAATPTSLLISWPYPRGPYVFYRITYGETGGNS his tag PVQEFTVYPGQATISGLKPGVDYTITVYAYTSGYVISINYRTEI  DKPSQHHHHHH 349 ATI_1422_F05 w/ N GVSDVPRDLEVVAATPTSLLISWPYPRGPYVFYRITYGETGGNS leader and C tail PVQEFTVYPGQATISGLKPGVDYTITVYAYTSGYVISINYRTEI  DKPSQ 350 ATI_1422_F05 w/ N leader GVSDVPRDLEVVAATPTSLLISWPYPRGPYVFYRITYGETGGNS and C tail + his tag PVQEFTVYPGQATISGLKPGVDYTITVYAYTSGYVISINYRTEI  DKPSQHHHHHH 351 ATI_1422_F05 w/ N leader GVSDVPRDLEVVAATPTSLLISWPYPRGPYVFYRITYGETGGNS and modified C-terminus PVQEFTVYPGQATISGLKPGVDYTITVYAYTSGYVISINYRTPC including PC 352 ATI_1422_F05 w/ N leader GVSDVPRDLEVVAATPTSLLISWPYPRGPYVFYRITYGETGGNS and modified C-terminus PVQEFTVYPGQATISGLKPGVDYTITVYAYTSGYVISINYRTPC including PC + his tag HHHHHH 353 ATI_1422_F05-full length MGVSDVPRDLEVVAATPTSLLISWPYPRGPYVFYRITYGETGGN SPVQEFTVYPGQATISGLKPGVDYTITVYAYTSGYVISINYRTE IDKPSQHHHHHH 354 ATI_1422_H04 core EVVAATPTSLLISWYLPSYYVQYRITYGETGGNSPVQEFTVKSY NATISGLKPGVDYTITVYARMGVYYLSYSISINYRT 355 ATI_1422_H04 BC loop YLPSYYVQ 356 ATI_1422_H04 DE loop KSYN 357 ATI_1422_H04 FG loop RMGVYYLSYS 358 ATI_1422_H04 w/ N GVSDVPRDLEVVAATPTSLLISWYLPSYYVQYRITYGETGGNSP  leader VQEFTVKSYNATISGLKPGVDYTITVYARMGVYYLSYSISINYR T 359 ATI_1422_H04 w/ N GVSDVPRDLEVVAATPTSLLISWYLPSYYVQYRITYGETGGNSP  leader + his tag VQEFTVKSYNATISGLKPGVDYTITVYARMGVYYLSYSISINYR THHHHHH 360 ATI_1422_H04 w/ N GVSDVPRDLEVVAATPTSLLISWYLPSYYVQYRITYGETGGNSP  leader and C tail VQEFTVKSYNATISGLKPGVDYTITVYARMGVYYLSYSISINYR TEIDKPSQ 361 ATI_1422_H04 w/ N GVSDVPRDLEVVAATPTSLLISWYLPSYYVQYRITYGETGGNSP  leader and C tail +  VQEFTVKSYNATISGLKPGVDYTITVYARMGVYYLSYSISINYR his tag TEIDKPSQHHHHHH 362 ATI_1422_H04 w/ N GVSDVPRDLEVVAATPTSLLISWYLPSYYVQYRITYGETGGNSP  leader and modified C- VQEFTVKSYNATISGLKPGVDYTITVYARMGVYYLSYSISINYR terminus including PC TPC 363 ATI_1422_H04 w/ N GVSDVPRDLEVVAATPTSLLISWYLPSYYVQYRITYGETGGNSP  leader and modified C- VQEFTVKSYNATISGLKPGVDYTITVYARMGVYYLSYSISINYR terminus including PC + TPCHHHHHH his tag 364 ATI_1422_H04-full MGVSDVPRDLEVVAATPTSLLISWYLPSYYVQYRITYGETGGNS length PVQEFTVKSYNATISGLKPGVDYTITVYARMGVYYLSYSISINY RTEIDKPSQHHHHHH 365 ATI_1422_H05 core EVVAATPTSLLISWQGQLSPSFYRITYGETGGNSPVQEFTVVAG MATISGLKPGVDYTITVYATSDVYFYSISINYRT 366 ATI_1422_H05 BC loop QGQLSPSF 367 ATI_1422_H05 DE loop VAGM 368 ATI_1422_H05 FG loop TSDVYFYS 369 ATI_1422_H05 w/ N GVSDVPRDLEVVAATPTSLLISWQGQLSPSFYRITYGETGGNSP  leader VQEFTVVAGMATISGLKPGVDYTITVYATSDVYFYSISINYRT 370 ATI_1422_H05 w/ N GVSDVPRDLEVVAATPTSLLISWQGQLSPSFYRITYGETGGNSP  leader + his tag VQEFTVVAGMATISGLKPGVDYTITVYATSDVYFYSISINYRTH HHHHH 371 ATI_1422_H05 w/ N GVSDVPRDLEVVAATPTSLLISWQGQLSPSFYRITYGETGGNSP  leader and C tail VQEFTVVAGMATISGLKPGVDYTITVYATSDVYFYSISINYRTE IDKPSQ 372 ATI_1422_H05 w/ N GVSDVPRDLEVVAATPTSLLISWQGQLSPSFYRITYGETGGNSP  leader and C tail +  VQEFTVVAGMATISGLKPGVDYTITVYATSDVYFYSISINYRTE his tag IDKPSQHHHHHH 373 ATI_1422_H05 w/ N GVSDVPRDLEVVAATPTSLLISWQGQLSPSFYRITYGETGGNSP  leader and modified C- VQEFTVVAGMATISGLKPGVDYTITVYATSDVYFYSISINYRTP  terminus including PC C 374 ATI_1422_H05 w/ N GVSDVPRDLEVVAATPTSLLISWQGQLSPSFYRITYGETGGNSP  leader and modified C- VQEFTVVAGMATISGLKPGVDYTITVYATSDVYFYSISINYRTP  terminus including PC + CHHHHHH his tag 375 -full length MGVSDVPRDLEVVAATPTSLLISWQGQLSPSFYRITYGETGGNS PVQEFTVVAGMATISGLKPGVDYTITVYATSDVYFYSISINYRT EIDKPSQHHHHHH 376 ATI_1422_G05 core EVVAATPTSLLISWIAPYYSVIYRITYGETGGNSPVQEFTVTGS GYATISGLKPGVDYTITVYATYCASVASYAFISINYRT 377 ATI_1422_G05 BC loop IAPYYSVI 378 ATI_1422_G05 DE loop TGSGY 379 ATI_1422_G05 FG loop TYCASVASYAF 380 ATI_1422_G05 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNSP  leader VQEFTVTGSGYATISGLKPGVDYTITVYATYCASVASYAFISIN YRT 381 ATI_1422_G05 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNSP  leader + his tag VQEFTVTGSGYATISGLKPGVDYTITVYATYCASVASYAFISIN YRTHHHHHH 382 ATI_1422_G05 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNSP  leader and C tail VQEFTVTGSGYATISGLKPGVDYTITVYATYCASVASYAFISIN YRTEIDKPSQ 383 ATI_1422_G05 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNSP  leader and C tail + his tag VQEFTVTGSGYATISGLKPGVDYTITVYATYCASVASYAFISIN YRTEIDKPSQHHHHHH 384 ATI_1422_G05 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNSP  leader and modified C- VQEFTVTGSGYATISGLKPGVDYTITVYATYCASVASYAFISIN terminus including PC YRTPC 385 ATI_1422_G05 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNSP  leader and modified C- VQEFTVTGSGYATISGLKPGVDYTITVYATYCASVASYAFISIN terminus including PC + YRTPCHHHHHH his tag 386 ATI_1422_G05-full MGVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNS length PVQEFTVTGSGYATISGLKPGVDYTITVYATYCASVASYAFISI  NYRTEIDKPSQHHHHHH 387 ATI_1760_C02 core EVVAATPTSLLISWIAPYYSVIYRITYGETGGNSPVQEFTVPGS AYATISGLKPGVDYTITVYASSGASIAAYAFISINYRT 388 ATI_1760 C02 BC loop IAPYYSVI 389 ATI_1760 C02 DE loop PGSAY 390 ATI_1760_C02 FG loop SSGASIAAYAF 391 ATI_1760_C02 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNSP  leader VQEFTVPGSAYATISGLKPGVDYTITVYASSGASIAAYAFISIN YRT 392 ATI_1760_C02 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNSP  leader + his tag VQEFTVPGSAYATISGLKPGVDYTITVYASSGASIAAYAFISIN YRTHHHHHH 393 ATI_1760_C02 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNSP  leader and C tail VQEFTVPGSAYATISGLKPGVDYTITVYASSGASIAAYAFISIN YRTEIDKPSQ 394 ATI_1760_C02 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNSP  leader and C tail +  VQEFTVPGSAYATISGLKPGVDYTITVYASSGASIAAYAFISIN his tag YRTEIDKPSQHHHHHH 395 ATI_1760_C02 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNSP  leader and modified C- VQEFTVPGSAYATISGLKPGVDYTITVYASSGASIAAYAFISIN terminus including PC YRTPC 396 ATI_1760_C02 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNSP  leader and modified C- VQEFTVPGSAYATISGLKPGVDYTITVYASSGASIAAYAFISIN terminus including PC + YRTPCHHHHHH his tag 397 ATI_1760_C02-full MGVSDVPRDLEVVAATPTSLLISWIAPYYSVIYRITYGETGGNS length PVQEFTVPGSAYATISGLKPGVDYTITVYASSGASIAAYAFISI  NYRTEIDKPSQHHHHHH 398 ATI_1760_E01 core EVVAATPTSLLISWIAPYYSVKYRITYGETGGNSPVQEFTVAGA DYATISGLKPGVDYTITVYATYGASIASYAFISINYRT 399 ATI_1760_E01 BC loop IAPYYSVK 400 ATI_1760_E01 DE loop AGADY 401 ATI_1760_E01 FG loop TYGASIASYAF 402 ATI_1760_E01 w/ N leader GVSDVPRDLEVVAATPTSLLISWIAPYYSVKYRITYGETGGNSP  VQEFTVAGADYATISGLKPGVDYTITVYATYGASIASYAFISIN YRT 403 ATI_1760_E01 w/ N leader + GVSDVPRDLEVVAATPTSLLISWIAPYYSVKYRITYGETGGNSP  his tag VQEFTVAGADYATISGLKPGVDYTITVYATYGASIASYAFISIN YRTHHHHHH 404 ATI_1760_E01 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYSVKYRITYGETGGNSP  leader and C tail VQEFTVAGADYATISGLKPGVDYTITVYATYGASIASYAFISIN YRTEIDKPSQ 405 ATI_1760_E01 w/ N leader GVSDVPRDLEVVAATPTSLLISWIAPYYSVKYRITYGETGGNSP  and C tail + his tag VQEFTVAGADYATISGLKPGVDYTITVYATYGASIASYAFISIN YRTEIDKPSQHHHHHH 406 ATI_1760_E01 w/ N leader GVSDVPRDLEVVAATPTSLLISWIAPYYSVKYRITYGETGGNSP  and modified C-terminus VQEFTVAGADYATISGLKPGVDYTITVYATYGASIASYAFISIN including PC YRTPC 407 ATI_1760_E01 w/ N leader GVSDVPRDLEVVAATPTSLLISWIAPYYSVKYRITYGETGGNSP  and modified C-terminus VQEFTVAGADYATISGLKPGVDYTITVYATYGASIASYAFISIN including PC + his tag YRTPCHHHHHH 408 ATI_1760_E01-full length MGVSDVPRDLEVVAATPTSLLISWIAPYYSVKYRITYGETGGNS PVQEFTVAGADYATISGLKPGVDYTITVYATYGASIASYAFISI  NYRTEIDKPSQHHHHHH 409 ATI_1760_F01 core EVVAATPTSLLISWIAPYYAVMYRITYGETGGNSPVQEFTVPGG GYATISGLKPGVDYTITVYATGGASIAAYAFISINYRT 410 ATI_1760_F01 BC loop IAPYYAVM 411 ATI_1760_F01 DE loop PGGGY 412 ATI_1760_F01 FG loop TGGASIAAYAF 413 ATI_1760_F01 w/ N leader GVSDVPRDLEVVAATPTSLLISWIAPYYAVMYRITYGETGGNSP  VQEFTVPGGGYATISGLKPGVDYTITVYATGGASIAAYAFISIN YRT 414 ATI_1760_F01 w/ N leader GVSDVPRDLEVVAATPTSLLISWIAPYYAVMYRITYGETGGNSP  + his tag VQEFTVPGGGYATISGLKPGVDYTITVYATGGASIAAYAFISIN YRTHHHHHH 415 ATI_1760_F01 w/ N GVSDVPRDLEVVAATPTSLLISWIAPYYAVMYRITYGETGGNSP  leader and C tail VQEFTVPGGGYATISGLKPGVDYTITVYATGGASIAAYAFISIN YRTEIDKPSQ 416 ATI_1760_F01 w/ N leader GVSDVPRDLEVVAATPTSLLISWIAPYYAVMYRITYGETGGNSP  and C tail + his tag VQEFTVPGGGYATISGLKPGVDYTITVYATGGASIAAYAFISIN YRTEIDKPSQHHHHHH 417 ATI_1760_F01 w/ N leader GVSDVPRDLEVVAATPTSLLISWIAPYYAVMYRITYGETGGNSP  and modified C-terminus VQEFTVPGGGYATISGLKPGVDYTITVYATGGASIAAYAFISIN including PC YRTPC 418 ATI_1760_F01 w/ N leader GVSDVPRDLEVVAATPTSLLISWIAPYYAVMYRITYGETGGNSP  and modified C-terminus VQEFTVPGGGYATISGLKPGVDYTITVYATGGASIAAYAFISIN including PC + his tag YRTPCHHHHHH 419 ATI_1760_F01-full length MGVSDVPRDLEVVAATPTSLLISWIAPYYAVMYRITYGETGGNS PVQEFTVPGGGYATISGLKPGVDYTITVYATGGASIAAYAFISI  NYRTEIDKPSQHHHHHH 420 ATI_1494_D03 core EVVAATPTSLLISWSYPSYHLYRITYGETGGNSPVQEFTVHIDY ATISGLKPGVDYTITVYAQSPPYDIYYEISINYRT 421 ATI_1494_D03 BC loop SYPSYHL 422 ATI_1494_D03 DE loop HIDY 423 ATI_1494_D03 FG loop QSPPYDIYYE 424 ATI_1494_D03 w/ N GVSDVPRDLEVVAATPTSLLISWSYPSYHLYRITYGETGGNSPV leader QEFTVHIDYATISGLKPGVDYTITVYAQSPPYDIYYEISINYRT 425 ATI_1494_D03 w/ N GVSDVPRDLEVVAATPTSLLISWSYPSYHLYRITYGETGGNSPV leader + his tag QEFTVHIDYATISGLKPGVDYTITVYAQSPPYDIYYEISINYRT HHHHHH 426 ATI_1494_D03 w/ N GVSDVPRDLEVVAATPTSLLISWSYPSYHLYRITYGETGGNSPV leader and C tail QEFTVHIDYATISGLKPGVDYTITVYAQSPPYDIYYEISINYRT EIDKPSQ 427 ATI_1494_D03 w/ N GVSDVPRDLEVVAATPTSLLISWSYPSYHLYRITYGETGGNSPV leader and C tail +  QEFTVHIDYATISGLKPGVDYTITVYAQSPPYDIYYEISINYRT his tag EIDKPSQHHHHHH 428 ATI_1494_D03 w/ N GVSDVPRDLEVVAATPTSLLISWSYPSYHLYRITYGETGGNSPV leader and modified C- QEFTVHIDYATISGLKPGVDYTITVYAQSPPYDIYYEISINYRT terminus including PC PC 429 ATI_1494_D03 w/ N GVSDVPRDLEVVAATPTSLLISWSYPSYHLYRITYGETGGNSPV leader and modified C- QEFTVHIDYATISGLKPGVDYTITVYAQSPPYDIYYEISINYRT terminus including PC + PCHHHHHH his tag 430 ATI_1494_D03-full MGVSDVPRDLEVVAATPTSLLISWSYPSYHLYRITYGETGGNSP  length VQEFTVHIDYATISGLKP TEIDKPSQHHHHHH 431 ATI_1494_D04 core EVVAATPTSLLISWMESSSNSYRITYGETGGNSPVQEFTVPDQL ATISGLKPGVDYTITVYALANAHYMRVGISINYRT 432 ATI_1494_D04 BC loop MESSSNS 433 ATI_1494_D04 DE loop PDQL 434 ATI_1494_D04 FG loop LANAHYMRVG 435 ATI_1494_D04 w/ N GVSDVPRDLEVVAATPTSLLISWMESSSNSYRITYGETGGNSPV leader QEFTVPDQLATISGLKPGVDYTITVYALANAHYMRVGISINYRT 436 ATI_1494_D04 w/ N GVSDVPRDLEVVAATPTSLLISWMESSSNSYRITYGETGGNSPV   leader + his tag QEFTVPDQLATISGLKPGVDYTITVYALANAHYMRVGISINYRT HHHHHH 437 ATI_1494_D04 w/ N GVSDVPRDLEVVAATPTSLLISWMESSSNSYRITYGETGGNSPV leader and C tail QEFTVPDQLATISGLKPGVDYTITVYALANAHYMRVGISINYRT EIDKPSQ 438 ATI_1494_D04 w/ N GVSDVPRDLEVVAATPTSLLISWMESSSNSYRITYGETGGNSPV leader and C tail +  QEFTVPDQLATISGLKPGVDYTITVYALANAHYMRVGISINYRT his tag EIDKPSQHHHHHH 439 ATI_1494_D04 w/ N GVSDVPRDLEVVAATPTSLLISWMESSSNSYRITYGETGGNSPV leader and modified C- QEFTVPDQLATISGLKPGVDYTITVYALANAHYMRVGISINYRT terminus including PC PC 440 ATI_1494_D04 w/ N GVSDVPRDLEVVAATPTSLLISWMESSSNSYRITYGETGGNSPV leader and modified C- QEFTVPDQLATISGLKPGVDYTITVYALANAHYMRVGISINYRT terminus including PC + PCHHHHHH his tag 441 ATI_1494_D04-full MGVSDVPRDLEVVAATPTSLLISWMESSSNSYRITYGETGGNSP  length VQEFTVPDQLATISGLKPGVDYTITVYALEKAHYYRQNISINYR TEIDKPSQHHHHHH 442 ATI_1523_A08 core EVVAATPTSLLISWISVQTYXYRITYGETGGNSPVQEFTVPDQS ATISGLKPGVDYTITVYALEKAHYYRQNISINYRT 443 ATI_1523_A08 BC loop ISVQTYX 444 ATI_1523_A08 DE loop PDQS 445 ATI_1523_A08 FG loop LEKAHYYRQN 446 ATI_1523_A08 w/ N GVSDVPRDLEVVAATPTSLLISWISVQTYXYRITYGETGGNSPV leader QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT 447 ATI_1523_A08 w/ N GVSDVPRDLEVVAATPTSLLISWISVQTYXYRITYGETGGNSPV leader + his tag QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT HHHHHH 448 ATI_1523_A08 w/ N GVSDVPRDLEVVAATPTSLLISWISVQTYXYRITYGETGGNSPV leader and C tail QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT EIDKPSQ 449 ATI_1523_A08 w/ N GVSDVPRDLEVVAATPTSLLISWISVQTYXYRITYGETGGNSPV leader and C tail +  QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT his tag EIDKPSQHHHHHH 450 ATI_1523_A08 w/ N GVSDVPRDLEVVAATPTSLLISWISVQTYXYRITYGETGGNSPV leader and modified C- QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT terminus including PC PC 451 ATI_1523_A08 w/ N GVSDVPRDLEVVAATPTSLLISWISVQTYXYRITYGETGGNSPV leader and modified C- QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT terminus including PC + PCHHHHHH his tag 452 ATI_1523_A08-full MGVSDVPRDLEVVAATPTSLLISWISVQTYXYRITYGETGGNSP  length VQEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYR TEIDKPSQHHHHHH 453 ATI_1523_B10 core EVVAATPTSLLISWVYHYDXQYRITYGETGGNSPVQEFTVPDQK ATISGLKPGVDYTITVYALSEAHHKRDSISINYRT 454 ATI_1523_B10 BC loop VYHYDXQ 455 ATI_1523_B10 DE loop PDQK 456 ATI_1523_B10 FG loop LSEAHHKRDS 457 ATI_1523_B10 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDXQYRITYGETGGNSPV leader QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT 458 ATI_1523_B10 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDXQYRITYGETGGNSPV leader + his tag QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT HHHHHH 459 ATI_1523_B10 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDXQYRITYGETGGNSPV leader and C tail QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT EIDKPSQ 460 ATI_1523_B10 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDXQYRITYGETGGNSPV leader and C tail +  QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT his tag EIDKPSQHHHHHH 461 ATI_1523_B10 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDXQYRITYGETGGNSPV leader and modified C- QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT terminus including PC PC 462 ATI_1523_B10 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDXQYRITYGETGGNSPV leader and modified C- QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT terminus including PC + PCHHHHHH his tag 463 ATI_1523_B10-full MGVSDVPRDLEVVAATPTSLLISWVYHYDXQYRITYGETGGNSP  length VQEFTVPDQKATISGLKP TEIDKPSQHHHHHH 464 ATI_1523_C07 core EVVAATPTSLLISWRMHTDPDYRITYGETGGNSPVQEFTVPDQE ATISGLKPGVDYTITVYAIQTAHYYRINISINYRT 465 ATI_1523_C07 BC loop RMHTDPD 466 ATI_1523 CO7 DE loop PDQE 467 ATI_1523 CO7 FG loop IQTAHYYRIN 468 ATI_1523_C07 w/ N GVSDVPRDLEVVAATPTSLLISWRMHTDPDYRITYGETGGNSPV leader QEFTVPDQEATISGLKPGVDYTITVYAIQTAHYYRINISINYRT 469 ATI_1523_C07 w/ N GVSDVPRDLEVVAATPTSLLISWRMHTDPDYRITYGETGGNSPV leader + his tag QEFTVPDQEATISGLKPGVDYTITVYAIQTAHYYRINISINYRT HHHHHH 470 ATI_1523_C07 w/ N GVSDVPRDLEVVAATPTSLLISWRMHTDPDYRITYGETGGNSPV leader and C tail QEFTVPDQEATISGLKPGVDYTITVYAIQTAHYYRINISINYRT EIDKPSQ 471 ATI_1523_C07 w/ N GVSDVPRDLEVVAATPTSLLISWRMHTDPDYRITYGETGGNSPV leader and C tail +  QEFTVPDQEATISGLKPGVDYTITVYAIQTAHYYRINISINYRT his tag EIDKPSQHHHHHH 472 ATI_1523_C07 w/ N GVSDVPRDLEVVAATPTSLLISWRMHTDPDYRITYGETGGNSPV leader and modified C- QEFTVPDQEATISGLKPGVDYTITVYAIQTAHYYRINISINYRT terminus including PC PC 473 ATI_1523_C07 w/ N GVSDVPRDLEVVAATPTSLLISWRMHTDPDYRITYGETGGNSPV leader and modified C- QEFTVPDQEATISGLKPGVDYTITVYAIQTAHYYRINISINYRT terminus including PC + PCHHHHHH his tag 474 ATI_1523_C07-full MGVSDVPRDLEVVAATPTSLLISWRMHTDPDYRITYGETGGNSP  length VQEFTVPDQEATISGLKPGVDYTITVYAIQTAHYYRINISINYR TEIDKPSQHHHHHH 475 ATI_1523_D07 core EVVAATPTSLLISWENLASYQYRITYGETGGNSPVQEFTVPDVQ ATISGLKPGVDYTITVYALPYIHMKQRVISINYRT 476 ATI_1523_D07 BC loop ENLASYQ 477 ATI_1523_D07 DE loop PDVQ 478 ATI_1523_D07 FG loop LPYIHMKQRV 479 ATI_1523_D07 w/ N GVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSPV leader QEFTVPDVQATISGLKPGVDYTITVYALPYIHMKQRVISINYRT 480 ATI_1523_D07 w/ N GVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSPV leader + his tag QEFTVPDVQATISGLKPGVDYTITVYALPYIHMKQRVISINYRT HHHHHH 481 ATI_1523_D07 w/ N GVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSPV leader and C tail QEFTVPDVQATISGLKPGVDYTITVYALPYIHMKQRVISINYRT EIDKPSQ 482 ATI_1523_D07 w/ N GVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSPV leader and C tail +  QEFTVPDVQATISGLKPGVDYTITVYALPYIHMKQRVISINYRT his tag EIDKPSQHHHHHH 483 ATI_1523_D07 w/ N GVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSPV leader and modified C- QEFTVPDVQATISGLKPGVDYTITVYALPYIHMKQRVISINYRT terminus including PC PC 484 ATI_1523_D07 w/ N GVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSPV leader and modified C- QEFTVPDVQATISGLKPGVDYTITVYALPYIHMKQRVISINYRT terminus including PC + PCHHHHHH his tag 485 ATI_1523_D07-full MGVSDVPRDLEVVAATPTSLLISWENLASYQYRITYGETGGNSP  length VQEFTVPDVQATISGLKPGVDYTITVYALPYIHMKQRVISINYR TEIDKPSQHHHHHH 486 ATI_1523_D08 core EVVAATPTSLLISWMRYYDAYYRITYGETGGNSPVQEFTVPDQS ATISGLKPGVDYTITVYALEKAHYYRQNISINYRT 487 ATI_1523_D08 BC loop MRYYDAY 488 ATI_1523_D08 DE loop PDQS 489 ATI_1523_D08 FG loop LEKAHYYRQN 490 ATI_1523_D08 w/ N GVSDVPRDLEVVAATPTSLLISWMRYYDAYYRITYGETGGNSPV leader QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT 491 ATI_1523_D08 w/ N GVSDVPRDLEVVAATPTSLLISWMRYYDAYYRITYGETGGNSPV leader + his tag QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT HHHHHH 492 ATI_1523_D08 w/ N GVSDVPRDLEVVAATPTSLLISWMRYYDAYYRITYGETGGNSPV leader and C tail QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT EIDKPSQ 493 ATI_1523_D08 w/ N GVSDVPRDLEVVAATPTSLLISWMRYYDAYYRITYGETGGNSPV leader and C tail + his tag QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT EIDKPSQHHHHHH 494 ATI_1523_D08 w/ N GVSDVPRDLEVVAATPTSLLISWMRYYDAYYRITYGETGGNSPV leader and modified C- QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT terminus including PC PC 495 ATI_1523_D08 w/ N GVSDVPRDLEVVAATPTSLLISWMRYYDAYYRITYGETGGNSPV leader and modified C- QEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYRT terminus including PC + PCHHHHHH his tag 496 ATI_1523_D08-full MGVSDVPRDLEVVAATPTSLLISWMRYYDAYYRITYGETGGNSP  length VQEFTVPDQSATISGLKPGVDYTITVYALEKAHYYRQNISINYR TEIDKPSQHHHHHH 497 ATI_1523_E08 core EVVAATPTSLLISWHHYQHYEYRITYGETGGNSPVQEFTVPDMG ATISGLKPGVDYTITVYALEEAHSDRSSISINYRT 498 ATI_1523_E08 BC loop HHYQHYE 499 ATI_1523_E08 DE loop PDMG 500 ATI_1523_E08 FG loop LEEAHSDRSS 501 ATI_1523_E08 w/ N leader GVSDVPRDLEVVAATPTSLLISWHHYQHYEYRITYGETGGNSPV QEFTVPDMGATISGLKPGVDYTITVYALEEAHSDRSISINYRT 502 ATI_1523_E08 w/ N leader + GVSDVPRDLEVVAATPTSLLISWHHYQHYEYRITYGETGGNSPV his tag QEFTVPDMGATISGLKPGVDYTITVYALEEAHSDRSISINYRT HHHHHH 503 ATI_1523_E08 w/ N leader GVSDVPRDLEVVAATPTSLLISWHHYQHYEYRITYGETGGNSPV and C tail QEFTVPDMGATISGLKPGVDYTITVYALEEAHSDRSISINYRT EIDKPSQ 504 ATI_1523_E08 w/ N leader GVSDVPRDLEVVAATPTSLLISWHHYQHYEYRITYGETGGNSPV and C tail + his tag QEFTVPDMGATISGLKPGVDYTITVYALEEAHSDRSISINYRT EIDKPSQHHHHHH 505 ATI_1523_E08 w/ N leader GVSDVPRDLEVVAATPTSLLISWHHYQHYEYRITYGETGGNSPV and modified C-terminus QEFTVPDMGATISGLKPGVDYTITVYALEEAHSDRSISINYRT including PC PC 506 ATI_1523_E08 w/ N leader GVSDVPRDLEVVAATPTSLLISWHHYQHYEYRITYGETGGNSPV and modified C-terminus QEFTVPDMGATISGLKPGVDYTITVYALEEAHSDRSISINYRT including PC + his tag PCHHHHHH 507 ATI_1523_E08-full length  MGVSDVPRDLEVVAATPTSLLISWHHYQHYEYRITYGETGGNSP  VQEFTVPDMGATISGLKPGVDYTITVYALEEAHSDRSISINYR TEIDKPSQHHHHHH 508 ATI_1523_F01 core EVVAATPTSLLISWYKPSTIVTYRITYGETGGNSPVQEFTVYGY NATISGLKPGVDYTITVYAVHGVRFISINYRT 509 ATI_1523_F01 BC loop YKPSTIVT 510 ATI_1523_F01 DE loop YGYN 511 ATI_1523_F01 FG loop VHGVRF 512 ATI_1523_F01 w/ N leader GVSDVPRDLEVVAATPTSLLISWYKPSTIVTYRITYGETGGNSP  VQEFTVYGYNATISGLKPGVDYTITVYAVHGVRFISINYRT 513 ATI_1523_F01 w/ N leader +  GVSDVPRDLEVVAATPTSLLISWYKPSTIVTYRITYGETGGNSP  his tag VQEFTVYGYNATISGLKPGVDYTITVYAVHGVRFISINYRTHHH HHH 514 ATI_1523_F01 w/ N leader GVSDVPRDLEVVAATPTSLLISWYKPSTIVTYRITYGETGGNSP  and C tail VQEFTVYGYNATISGLKPGVDYTITVYAVHGVRFISINYRTEID KPSQ 515 ATI_1523_F01 w/ N leader GVSDVPRDLEVVAATPTSLLISWYKPSTIVTYRITYGETGGNSP  and C tail + his tag VQEFTVYGYNATISGLKPGVDYTITVYAVHGVRFISINYRTEID KPSQHHHHHH 516 ATI_1523_F01 w/ N leader GVSDVPRDLEVVAATPTSLLISWYKPSTIVTYRITYGETGGNSP  and modified C-terminus VQEFTVYGYNATISGLKPGVDYTITVYAVHGVRFISINYRTPC including PC 517 ATI_1523_F01 w/ N leader GVSDVPRDLEVVAATPTSLLISWYKPSTIVTYRITYGETGGNSP  and modified C-terminus VQEFTVYGYNATISGLKPGVDYTITVYAVHGVRFISINYRTPCH including PC + his tag HHHHH 518 ATI_1523_F01-full length  MGVSDVPRDLEVVAATPTSLLISWYKPSTIVTYRITYGETGGNS PVQEFTVYGYNATISGLKPGVDYTITVYAVHGVRFISINYRTEI  DKPSQHHHHHH 519 ATI_1523_F04 core EVVAATPTSLLISWGGSLSPTFYRITYGETGGNSPVQEFTVTYQ GATISGLKPGVDYTITVYATEGIVYYQISINYRT 520 ATI_1523_F04 BC loop GGSLSPTF 521 ATI_1523_F04 DE loop TYQG 522 ATI_1523_F04 FG loop TEGIVYYQ 523 ATI_1523_F04 w/ N leader GVSDVPRDLEVVAATPTSLLISWGGSLSPTFYRITYGETGGNSP  VQEFTVTYQGATISGLKPGVDYTITVYATEGIVYYQISINYRT 524 ATI_1523_F04 w/ N leader +  GVSDVPRDLEVVAATPTSLLISWGGSLSPTFYRITYGETGGNSP  his tag VQEFTVTYQGATISGLKPGVDYTITVYATEGIVYYQISINYRTH HHHHH 525 ATI_1523_F04 w/ N leader GVSDVPRDLEVVAATPTSLLISWGGSLSPTFYRITYGETGGNSP  and C tail VQEFTVTYQGATISGLKPGVDYTITVYATEGIVYYQISINYRTE IDKPSQ 526 ATI_1523_F04 w/ N leader GVSDVPRDLEVVAATPTSLLISWGGSLSPTFYRITYGETGGNSP  and C tail + his tag VQEFTVTYQGATISGLKPGVDYTITVYATEGIVYYQISINYRTE IDKPSQHHHHHH 527 ATI_1523_F04 w/ N leader GVSDVPRDLEVVAATPTSLLISWGGSLSPTFYRITYGETGGNSP  and modified C-terminus VQEFTVTYQGATISGLKPGVDYTITVYATEGIVYYQISINYRTP  including PC C 528 ATI_1523_F04 w/ N leader GVSDVPRDLEVVAATPTSLLISWGGSLSPTFYRITYGETGGNSP  and modified C-terminus VQEFTVTYQGATISGLKPGVDYTITVYATEGIVYYQISINYRTP  including PC + his tag CHHHHHH 529 ATI_1523_F04-full length  MGVSDVPRDLEVVAATPTSLLISWGGSLSPTFYRITYGETGGNS PVQEFTVTYQGATISGLKPGVDYTITVYATEGIVYYQISINYRT EIDKPSQHHHHHH 530 ATI_1523_F08 core EVVAATPTSLLISWVYHYDAQYRITYGETGGNSPVQEFTVPDQK ATISGLKPGVDYTITVYALPRAHMDRSHISINYRT 531 ATI_1523_F08 BC loop VYHYDAQ 532 ATI_1523_F08 DE loop PDQK 533 ATI_1523_F08 FG loop LPRAHMDRSH 534 ATI_1523_F08 w/ N leader GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV QEFTVPDQKATISGLKPGVDYTITVYALPRAHMDRSHISINYRT 535 ATI_1523_F08 w/ N leader +  GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV his tag QEFTVPDQKATISGLKPGVDYTITVYALPRAHMDRSHISINYRT HHHHHH 536 ATI_1523_F08 w/ N leader GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV and C tail QEFTVPDQKATISGLKPGVDYTITVYALPRAHMDRSHISINYRT EIDKPSQ 537 ATI_1523_F08 w/ N leader GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV and C tail + his tag QEFTVPDQKATISGLKPGVDYTITVYALPRAHMDRSHISINYRT EIDKPSQHHHHHH 538 ATI_1523_F08 w/ N leader GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV and modified C-terminus QEFTVPDQKATISGLKPGVDYTITVYALPRAHMDRSHISINYRT including PC PC 539 ATI_1523_F08 w/ N leader GVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSPV and modified C-terminus QEFTVPDQKATISGLKPGVDYTITVYALPRAHMDRSHISINYRT including PC + his tag PCHHHHHH 540 ATI_1523_F08-full length  MGVSDVPRDLEVVAATPTSLLISWVYHYDAQYRITYGETGGNSP  VQEFTVPDQKATISGLKPGVDYTITVYALPRAHMDRSHISINYR TEIDKPSQHHHHHH 541 ATI_1523_G06 core EVVAATPTSLLISWRIKSYHKYRITYGETGGNSPVQEFTVRSYA ATISGLKPGVDYTITVYAIMEETHLAYAISINYRT 542 ATI_1523_G06 BC loop RIKSYHK 543 ATI_1523_G06 DE loop RSYA 544 ATI_1523_G06 FG loop IMEETHLAYA 545 ATI_1523_G06 w/ N GVSDVPRDLEVVAATPTSLLISWRIKSYHKYRITYGETGGNSPV leader QEFTVRSYAATISGLKPGVDYTITVYAIMEETHLAYAISINYRT 546 ATI_1523_G06 w/ N GVSDVPRDLEVVAATPTSLLISWRIKSYHKYRITYGETGGNSPV leader + his tag QEFTVRSYAATISGLKPGVDYTITVYAIMEETHLAYAISINYRT HHHHHH 547 ATI_1523_G06 w/ N GVSDVPRDLEVVAATPTSLLISWRIKSYHKYRITYGETGGNSPV leader and C tail QEFTVRSYAATISGLKPGVDYTITVYAIMEETHLAYAISINYRT EIDKPSQ 548 ATI_1523_G06 w/ N GVSDVPRDLEVVAATPTSLLISWRIKSYHKYRITYGETGGNSPV leader and C tail +  QEFTVRSYAATISGLKPGVDYTITVYAIMEETHLAYAISINYRT his tag EIDKPSQHHHHHH 549 ATI_1523_G06 w/ N GVSDVPRDLEVVAATPTSLLISWRIKSYHKYRITYGETGGNSPV leader and modified C- QEFTVRSYAATISGLKPGVDYTITVYAIMEETHLAYAISINYRT terminus including PC PC 550 ATI_1523_G06 w/ N GVSDVPRDLEVVAATPTSLLISWRIKSYHKYRITYGETGGNSPV leader and modified C- QEFTVRSYAATISGLKPGVDYTITVYAIMEETHLAYAISINYRT terminus including PC + PCHHHHHH his tag 551 ATI_1523_G06-full MGVSDVPRDLEVVAATPTSLLISWRIKSYHKYRITYGETGGNSP  length VQEFTVRSYAATISGLKPGVDYTITVYAIMEETHLAYAISINYR TEIDKPSQHHHHHH 552 ATI_1523_G07 core EVVAATPTSLLISWVYPQADDYRITYGETGGNSPVQEFTVPDQN ATISGLKPGVDYTITVYALAEAHLVRIYISINYRT 553 ATI_1523_G07 BC loop VYPQADD 554 ATI_1523_G07 DE loop PDQN 555 ATI_1523_G07 FG loop LAEAHLVRIY 556 ATI_1523_G07 w/ N GVSDVPRDLEVVAATPTSLLISWVYPQADDYRITYGETGGNSPV leader QEFTVPDQNATISGLKPGVDYTITVYALAEAHLVRIYISINYRT 557 ATI_1523_G07 w/ N GVSDVPRDLEVVAATPTSLLISWVYPQADDYRITYGETGGNSPV leader + his tag QEFTVPDQNATISGLKPGVDYTITVYALAEAHLVRIYISINYRT HHHHHH 558 ATI_1523_G07 w/ N GVSDVPRDLEVVAATPTSLLISWVYPQADDYRITYGETGGNSPV leader and C tail QEFTVPDQNATISGLKPGVDYTITVYALAEAHLVRIYISINYRT EIDKPSQ 559 ATI_1523_G07 w/ N GVSDVPRDLEVVAATPTSLLISWVYPQADDYRITYGETGGNSPV leader and C tail +  QEFTVPDQNATISGLKPGVDYTITVYALAEAHLVRIYISINYRT his tag EIDKPSQHHHHHH 560 ATI_1523_G07 w/ N GVSDVPRDLEVVAATPTSLLISWVYPQADDYRITYGETGGNSPV leader and modified C- QEFTVPDQNATISGLKPGVDYTITVYALAEAHLVRIYISINYRT terminus including PC PC 561 ATI_1523_G07 w/ N GVSDVPRDLEVVAATPTSLLISWVYPQADDYRITYGETGGNSPV leader and modified C- QEFTVPDQNATISGLKPGVDYTITVYALAEAHLVRIYISINYRT terminus including PC + PCHHHHHH his tag 562 ATI_1523_G07-full MGVSDVPRDLEVVAATPTSLLISWVYPQADDYRITYGETGGNSP  length VQEFTVPDQNATISGLKPGVDYTITVYALAEAHLVRIYISINYR TEIDKPSQHHHHHH 563 ATI_1523_H07 core EVVAATPTSLLISWVYHYDAXYRITYGETGGNSPVQEFTVPDQK ATISGLKPGVDYTITVYALSEAHHKRDSISINYRT 564 ATI_1523_H07 BC loop VYHYDAX 565 ATI_1523_H07 DE loop PDQK 566 ATI_1523_H07 FG loop LSEAHHKRDS 567 ATI_1523_H07 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDAXYRITYGETGGNSPV leader  QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT 568 ATI_1523_H07 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDAXYRITYGETGGNSPV leader + his tag QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT HHHHHH 569 ATI_1523_H07 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDAXYRITYGETGGNSPV leader and C tail QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT EIDKPSQ 570 ATI_1523_H07 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDAXYRITYGETGGNSPV leader and C tail +  QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT his tag EIDKPSQHHHHHH 571 ATI_1523_H07 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDAXYRITYGETGGNSPV leader and modified C- QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT terminus including PC PC 572 ATI_1523_H07 w/ N GVSDVPRDLEVVAATPTSLLISWVYHYDAXYRITYGETGGNSPV leader and modified C- QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT terminus including PC + PCHHHHHH his tag 573 ATI_1523_H07-full- GVSDVPRDLEVVAATPTSLLISWVYHYDAXYRITYGETGGNSPV length QEFTVPDQKATISGLKPGVDYTITVYALSEAHHKRDSISINYRT EIDKPSQHHHHHH 574 N-terminal leader MGVSDVPRDL 575 N-terminal leader GVSDVPRDL 576 N-terminal leader X_(n)SDVPRDL 577 N-terminal leader X_(n)DVPRDL 578 N-terminal leader X_(n)VPRDL 579 N-terminal leader X_(n)PRDL 580 N-terminal leader X_(n)RDL 581 N-terminal leader X_(n)DL 582 N-terminal leader MASTSG 583 N-terminal leader METDTLLLWVLLLWVPGSTG 584 C-terminal tail EIEK 585 C-terminal tail EGSGC 586 C-terminal tail EIEKPCQ 587 C-terminal tail EIEKPSQ 588 C-terminal tail EIEKP  589 C-terminal tail EIEKPS 590 C-terminal tail EIEKPC 591 C-terminal tail EIDK 592 C-terminal tail EIDKPCQ 593 C-terminal tail EIDKPSQ 594 C-terminal tail EIEPKSS 595 C-terminal tail EIDKPC 596 C-terminal tail EIDKP  597 C-terminal tail EIDKPS 598 C-terminal tail EIDKPSQLE 599 C-terminal tail EIEDEDEDEDED 600 C-terminal tail EGSGS 601 C-terminal tail EIDKPCQLE 602 C-terminal tail EIDKPSQHHHHHH 603 C-terminal tail GSGCHHHHHH 604 C-terminal tail EGSGCHHHHHH 605 C-terminal tail PIDK 606 C-terminal tail PIEK 607 C-terminal tail PIDKP  608 C-terminal tail PIEKP  609 C-terminal tail PIDKPS 610 C-terminal tail PIEKPS 611 C-terminal tail PIDKPC 612 C-terminal tail PIEKPC 613 C-terminal tail PIDKPSQ 614 C-terminal tail PIEKPSQ 615 C-terminal tail PIDKPCQ 616 C-terminal tail PIEKPCQ 617 C-terminal tail PHHHHHH 618 C-terminal tail PCHHHHHH 619 6X-His tag HHHHHH 620 Human IgG1 Fc domain DKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDV SHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQD WLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDEL ITKNQVSLTCLVKGFYPSDAVEWESNGQPENNYKTTPPVLDSDGSF FLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK 621 Core hinge region of Fc DKTHTCPPCPAPELLG 622 Exemplary hinge sequence EPKSSDKTHTCPPCPAPELLGGPS 623 Exemplary hinge sequence EPKSSDKTHTCPPCPAPELLGGSS 624 Exemplary hinge sequence EPKSSGSTHTCPPCPAPELLGGSS 625 Exemplary hinge sequence DKTHTCPPCPAPELLGGPS 626 Exemplary hinge sequence DKTHTCPPCPAPELLGGSS 627 Fc with CH2 and CH3 VFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVH regions of IgG1 for NAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAP Adnectin-hinge-Fc IEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDI construct AVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVF SCSVMHEALHNHYTQKSLSLSPGK 628 Fc with CH2 and CH3 VFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVH regions of IgG1 for Fc- NAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAP  hinge-Adnectin construct IEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDI AVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVF SCSVMHEALHNHYTQKSLSLSP  629 Linker 1 GAGGGGSG 630 Linker 2 EPKSD 631 Linker 3 PVGVV 632 Linker 4 ESPKAQASSVPTAQPQAEGLA 633 Linker 5 ELQLEESAAEAQDGELD 634 Linker 6 GQPDEPGGS 635 Linker 7 GGSGSGSGSGSGS 636 Linker 8 ELQLEESAAEAQEGELE 637 Linker 9 GSGSG 638 Linker 10 GSGC 639 Linker 11 AGGGGSG 640 Linker 12 GSGS 641 Linker 13 QPDEPGGS 642 Linker 14 GSGSGS 643 Linker 15 TVAAPS 644 Linker 16 KAGGGGSG 645 Linker 17 KGSGSGSGSGSGS 646 Linker 18 KQPDEPGGS 647 Linker 19 KELQLEESAAEAQDGELD 648 Linker 20 KTVAAPS 649 Linker 21 KAGGGGSGG 650 Linker 22 KGSGSGSGSGSGSG 651 Linker 23 KQPDEPGGSG 652 Linker 24 KELQLEESAAEAQDGELDG 653 Linker 25 KTVAAPSG 654 Linker 26 AGGGGSGG 655 Linker 27 AGGGGSG 656 Linker 28 GSGSGSGSGSGSG 657 Linker 29 QPDEPGGSG 658 Linker 30 TVAAPSG 659 Linker 31 PSTSTST 660 Linker 32 EIDKPSQ 661 Linker 33 GSGSGSGS 662 Linker 34 GSGSGSGSGS 663 Linker 35 GSGSGSGSGSGS 664 Linker 36 GSGSGSGSGSGSGS 665 Linker 37 GGSGSGSGSGSGS 666 Linker 38 GGSGSGSGSGSGSGSG 667 Linker 39 GSEGSEGSEGSEGSE 668 Linker 40 GGSEGGSE 669 Linker 41 GGGGSGGGGSGGGGSGGGGSGGGGSGGGGSGGGGS 670 Linker 42 GGGGSGGGGSGGGGSGGGGSGGGGS 671 Linker 43 GGGGSGGGGSGGGGSG 672 Linker 44 GPGPGPG 673 Linker 45 GPGPGPGPGPG 674 Linker 46 PAPAPA 675 Linker 47 PAPAPAPAPAPA 676 Linker 48 PAPAPAPAPAPAPAPAPA 677 Linker 49 GSGSGSGSGSGSGSGSGSGS 678 Linker 50 GGGGSGGGGSGGGGSGGGGS

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents of the specific embodiments described herein. Such equivalents are intended to be encompassed by the following claims. 

We claim:
 1. A method of visualizing Programmed Death Ligand-1 (PD-L1) protein in a subject, comprising: (a) administering to the subject a radiolabeled PD-L1 imaging agent at a dose of about 3-10 mCi (100-333 MBq); (b) conducting a PET scan of the subject about 30-120 minutes after administering the imaging agent and obtaining an image; and (c) visualizing the presence of the PD-L1 protein in the subject from the image, wherein the imaging agent comprises a radiolabeled prosthetic group conjugated to an anti-PD-L1 adnectin by a bifunctional chelating agent, wherein the radiolabeled prosthetic group has the following structure:

wherein the ¹⁸F is ortho to the N atom, x is an integer from 1 to 8, and wherein the anti-PD-L1 adnectin comprises BC, DE, and FG loops comprising amino acid sequences selected from the group consisting of: (i) SEQ ID NOs: 6, 7, and 8, respectively; (ii) SEQ ID NOs: 21, 22, and 23, respectively; (iii) SEQ ID NOs: 36, 37, and 38, respectively; (iv) SEQ ID NOs: 51, 52, and 53, respectively; (v) SEQ ID NOs: 66, 67, and 68, respectively; (vi) SEQ ID NOs: 81, 82, and 83, respectively; or (vii) SEQ ID NOs: 97, 98, and 99, respectively.
 2. The method of claim 1, wherein the subject has at least one tumor.
 3. The method of claim 2, comprising comparing the uptake of the imaging agent in the at least one tumor and in background tissue, wherein the presence of PD-L1 in the at least one tumor above the background tissue is indicative that the PD-L1 is expressed in the at least one tumor and that the subject is likely to respond to treatment with a PD-1 or PD-L1 antagonist.
 4. The method of claim 1, wherein the radiolabel is a radioactive PET tracer.
 5. The method of claim 1, wherein the anti-PD-L1 adnectin comprises an amino acid sequence at least 80% identical to an amino acid sequence selected from the group consisting of: SEQ ID NOs: 5, 20, 35, 50, 65, 80 or
 96. 6. The method of claim 1, wherein the anti-PD-L1 adnectin comprises an amino acid sequence at least 80% identical to an amino acid sequence selected from the group consisting of: SEQ ID NOs: 9-15, 24-30, 39-45, 54-60, 69-75, 84-91, and 100-107.
 7. The method of claim 1, wherein the structure of the ¹⁸F-radiolabeled prosthetic group is,


8. The method of claim 1, wherein the structure of the ¹⁸F-radiolabeled prosthetic group is,


9. The method of claim 1, wherein the structure of the ¹⁸F-radiolabeled prosthetic group is


10. The method of claim 1, wherein the bifunctional chelating agent is a cyclooctyne comprising a reactive group that forms a covalent bond with an amine, carboxyl, carbonyl or thiol functional group on the protein.
 11. The method of claim 1, wherein the imaging agent has a structure as set forth below:

wherein X is an anti-PD-L1 adnectin comprising the amino acid sequence of any one of SEQ ID NOs: 13, 28, 43, 58, 73, 88, and
 104. 12. The method of claim 11, wherein the anti-PD-L1 adnectin comprises the amino acid sequence set forth in SEQ ID NO:
 88. 13. The method of claim 11, wherein the anti-PD-L1 adnectin comprises the amino acid sequence set forth in SEQ ID NO:
 104. 